Second  Edition 
Price.  Two    Dollars 


Vitrified 
Paving  Brick 

A  Review  of  Present  Practice  in  the  Manufacture, 

Testing  and  Uses  of  Vitrified 

Paving  Brick. 


BY 

H.  A.  WHEELER,  E.  M., 

FORMER  CLAY'  SPECIALIST  OF  THE  MISSOURI 
GEOLOGICAL  SURVEY. 


S>     -      .       fvil-A 


INDIANAPOLIS,  IND., 

T.  A.  RANDALL  &  CO.,  PUBLISHERS. 

1910 


COPYRIGHTED, 

1910, 

BY  T.    A.    RANDALL  &  CO. 


TABLE    OF    CONTENTS. 

PAGE 

History  of  Paving  Brick 7 

Definition  of  Vitrified  Brick 10 

Clays  Employed 14 

Composition  of  Paving  Brick  Shales 17 

Physical  Properties  of  Clays 20 

Manufacture  of  Paving  Brick 23 

Winning  the  Clay 24 

Crushing    25 

Screening    26 

Pugging    26 

Molding    27 

Repressing    29 

Drying    30 

Burning   30 

Physical  Properties  of  Paving  Brick 35 

Color    35 

Structure   35 

Hardness    36 

Porosity   37 

Density    39 

Crushing    Strength 40 

Cross  Breaking  Strength 41 

Toughness  41 

Methods  of  Testing  Paving  Brick 49 

Eye  Examination 49 

Laboratory  Tests 50 

Density  51 

Absorption    52 

Crushing  Strength 54 

Cross    Breaking 54 

Hardness    55 

Rattler   Test 56 

Evaluation  of  the  Tests 58 

Uniformity  of  Results 58 

Uses  of  Vitrified  Brick 63 

Sewers    63 

Buildings    63 

Foundations    64 

Sidewalks    64 

Street   Paving 65 

Chemical  Purposes 65 

Other  Paving  Materials 65 


PAGE 

Macadam   66 

Wood    Pavements 67 

Asphalt  and  Bitulithic 68 

Granitoid   69 

Cobble  Stones 70 

Stone  Blocks 70 

Comparison  of  Street  Paving  Materials 71 

First    Cost 71 

Maintenance  72 

Traction   75 

Footing    76 

Cleanliness   76 

Noise    77 

Repairs    77 

Sanitary  Value 78 

Size  of  Brick 79 

Foundation   80 

Drumming  81 

Durability  of  Paving  Brick 82 

Paving   Statistics 84 

Specifications  for  Brick  Paving 86 

Grading  and  Preparing  the  Roadbed  for  Superstruc- 
ture        87 

Intersection  with  Streets  and  Alleys 88 

Cement : .     89 

Sand  and  Limestone  Screenings 90 

Broken  Stone  or  Washed  Gravel 90 

Concrete 91 

Crushing    91 

Vitrified  Brick  Wearing  Surface 93 

Guarantee    95 

General   Stipulations 99 

Payments    103 

N.  P.  B.  M.  A.  Specifications 107 

Grading 108 

Curbing 109 

Foundation   Ill 

Sand    Cushion 113 

Brick    114 

Bricklaying   115 

Rolling  and  Tamping 116 

Expansion    Cushion 117 

Filler    .  .  118 


PREFACE. 


Since  the  first  edition  of  this  booklet  was  published  in 
1895,  the  paving  brick  industry  has  developed  into  one  of  the 
large,  firmly  established  industries  of  this  country,  while  the 
merits  of  vitrified  brick  as  a  paving  material  are  now  so  uni- 
versally known  that  it  has  become  the  most  popular  of  pave- 
ments for  cities,  towns  and  even  counties. 

After  the  industry  got  a  successful  foothold  in  1885  there 
was  such  a  rapid  development  during  the  following  ten  years 
and  the  demand  and  prices  became  so  attractive  that  too  many 
brickmakers  rushed  into  the  new  and  enticing  field,  for  some 
were  inadequately  equipped  to  produce  a  good  paver,  or  their 
clay  was  not  suitable  to  make  a  durable  paver,  or,  under  the 
stimulus  of  growing  markets  and  increasing  prices  they  pur- 
sued the  short-sighted  policy  of  rushing  out  quantity,  imma- 
terial as  to  quality  of  the  brick.  In  consequence,  many  poor 
brick  were  put  on  the  market  at  a  time  when  the  public  was 
not  educated  to  distinguish  between  good,  indifferent  and 
bad  brick — a  paver  was  still  only  a  paver  to  most  consumers. 
There  was  also  a  woeful  lack  of  harmony  among  city  en- 
gineers as  to  what  constituted  a  good  paver,  how  to  lay  them 
and  how  to  test  them.  The  prompt  work  of  the  Testing  Com- 
mittee of  the  National  Brickmakers'  Association  soon  re- 
moved the  latter  confusion,  while  experience  more  slowly 
settled  the  former. 

This  setback,  of  which  full  advantage  was  taken  by  the 
competitors  of  brick,  was  not  without  its  salutary  effect,  and 
since  then  the  industry  has  been  established  on  a  more  con- 
servative, healthy  basis.  The  small,  imperfectly  equipped 
plants  have  been  succeeded  by  fewer  but  very  much  larger, 
well  equipped  factories  that  are  under  able  business  manage- 
ment, large  stocks  and  usually  several  grades  and  sizes  are 
carried,  while  the  inexorable  law  of  the  "survival  of  the  fit- 
test" has  eliminated  those  whose  clays  were  not  suitable. 


The  use  of  paving  brick  is  now  mainly  a  question  of 
freight.  The  weight  of  1,000  pavers  is  so  large,  from  four  to 
six  tons,  that  a  long  haul  greatly  increases  their  cost.  The 
use  of  brick  is,  therefore,  largely  confined  within  a  moderate 
radius  of  where  suitable  clays  occur-  Thus,  New  England, 
with  its  great  wealth  and  dense  population,  has  used  com- 
paratively little  brick  on  account  of  the  excessive  freight, 
while  local  macadam  is  usually  good  and  cheap.  The  state 
of  Ohio,  on  the  contrary,  with  its  great  abundance  of  suitable 
clays,  has  scarcely  a  town  of  500  that  has  not  at  least  paved 
its  main  street  with  brick. 

Vitrified  brick  is  now  exclusively  employed  in  many  of 
the  larger  cities  for  sewers,  for  which  its  exceptional  hard- 
ness pre-eminently  adapts  it,  while  its  use  is  steadily  grow- 
ing among  our  more  advanced  architects  for  the  exterior  of 
buildings,  for  under  skillful  handling  it  lends  itself  readily 
to  picturesque  effects  which  not  only  do  not  fade,  but  remain 
clean — a  feature  that  is  so  rare  in  any  other  building  ma- 
terial in  our  western  cities. 

Very  recently  a  careful  comparison  was  made  in  Indianap- 
olis (see  CLAY-WORKEB  August,  1909)  of  all  the  various  pav- 
ing materials  to  find  the  one  most  suitable  for  a  speedway 
for  automobiles.  After  elaborate  tests,  in  which  no  expense 
was  spared,  it  was  found  that  vitrified  brick  was  the  best. 
The  decision  is  too  recent  to  have  the  great  influence  that  it 
at  least  prognosticates  for  the  industry.  For,  with  the  very 
rapid  growth  in  the  use  of  the  automobile  and  its  increase  in 
power,  the  enormous  mileage  of  macadamized  roads  that  this 
popular  machine  has  developed  will  largely  give  way  to  brick, 
for  the  modern  automobile  is  found  to  rapidly  wear  and  heav- 
ily cut  into  even  well  maintained  macadam  roads. 

The  writer  takes  this  opportunity  to  express  his  thanks 
and  appreciation  to  the  many  engineers  who  favored  him 
with  local  data  and  their  personal  experience. 

St.  Louis,  Oct.  11,  1909.  H.  A.  WHEELER. 


HISTORY  OF  PAVING  BRICK. 


Brick  for  street  paving  has  been  in  use  for  more  than  a 
century  in  Holland,  where  the  absence  of  natural  paving  ma- 
terial developed  a  very  durable  quality  of  paving  brick  by 
mixing  the  fine  river  silt  or  mud  with  sand.  The  village  of 
Moor,  on  the  river  Yssel,  is  especially  famous  for  the  excel- 
lence of  its  brick  and  the  magnitude  of  its  paving  brick  in- 
dustry. 

To  a  much  less  extent  and  for  a  shorter  period,  they  have 
been  used  in  northern  England,  especially  in  Staffordshire  and 
Leeds;  under  the  name  of  "blue  brick"  and  "terro-metallic 
ware,"  where  their  application  is  restricted  more  to  stables, 
chemical  works  and  similar  places  where  a  non-absorbent 
brick  is  desired.  When  the  clay  is  not  readily  fusible,  slag, 
mill  cinder,  or  chalk  dust  is  added  in  English  practice  to  se- 
cure the  fluxing  or  vitrification  that  is  so  essential  in  this 
class  of  brick. 

Paving  brick  was  first  used  in  the  United  States  at 
Charleston,  W.  Va.,  in  1870,  a  town  of  12,000,  where  a  small 
section  was  laid  as  an  experiment.  This  proving  satisfactory, 
a  block  of  one  of  their  principal  streets  was  paved  in  1873,  in 
grading  for  which  it  was  necessary  to  take  up  the  small  sec- 
tion laid  in  1870.  This  is  still  in  use,  although  laid  on  a  poor 
foundation  of  boards,  and  while  the  street  has  been  repeated- 
ly torn  up  for  laying  pipe,  etc.,  it  is  still  in  fair  condition 
after  thirty-five  years'  service.  A  sample  of  this  brick  kindly 
sent  by  the  city  engineer,  Mr.  W.  A.  Hogue,  shows  it  to  be  a 
side-cut,  repressed,  hard  burned  building  brick  of  high  density, 


Development 
Abroad. 


Development   in 
the  United 
States. 


VITRIFIED    PAVING    BRICK. 


or  2.48,  and  it  absorbs  4.5  per  cent  on  soaking  twenty-four 
hours. 

Bloomington,  111.,  a  town  of  26,000,  laid  an  inferior  paving 
brick  in  1875,  on  one  of  their  principal  streets  that  lasted 
twenty  years  before  it  was  replaced  by  a  high  grade  shale 
paver.  A  sample  courteously  forwarded  by  Mr.  W.  P.  Butler, 
the  city  engineer,  shows  that  it  was  made  from  a  very  poor 
glacial  clay  by  the  "slop"  process  (or  from  a  very  soft  mud) 
by  hand  and  was  not  repressed.  It  shows  an  absorption  of 
4.33  per  cent  after  twenty-four  hours  immersion,  it  had  a 
density  of  2.11,  which  is  very  low,  and  it  showed  a  wear  of 
1  to  iy2  inches. 

St.  Louis  put  down  three  trial  lots  of  brick  paving  in  1880, 
one  of  which  was  the  result  of  experiments  dating  back  to 
1873,  the  Sattler  brick.  They  all  proved  failures,  from  being 
either  too  soft  or  too  brittle,  although  they  were  laid  on  a 
poor  foundation.  Another  lot  of  the  Sattler  brick  was  tried 
in  1881  that  was  successful,  but  the  maker  was  unable  to 
furnish  a  uniform,  reliable  brick,  as  he  used  a  fireclay  that 
was  too  refractory,  besides  having  other  manufacturing  diffi- 
culties. These  failures  made  such  a  bad  impression  on  the 
city  authorities,  although  made  in  the  infancy  of  the  indus- 
try and  before  any  first-class  pavers  had  been  produced  in 
this  country,  that  no  further  effort  was  made  to  use  brick 
until  1895.  Since  then  brick  has  not  only  become  very  popu- 
lar, but  today  is  used  almost  exclusively  on  the  residential 
and  semi-business  streets  and  alleys. 

Wheeling,  W.  Va.,  put  down  an  impure  fireclay  paving 
brick  in  1883  that  was  so  successful  as  to  make  this  one  of 
the  important  pioneers  of  the  paving  brick  industry,  from  the 
confidence  it  inspired;  some  of  these  brick  are  still  in  use, 
although  most  of  them  were  renewed  after  twenty  years. 

Decatur,   111.,   also   put  down  a   vitrified  brick  this   same 


VITRIFIED    PAVING    BRICK. 


year  that  was  made  from  a  glacial  clay,  which  is  still  in  use 
after  twenty-six  years'  service. 

Galesburg,  111.,  the  nestor  of  the  shale  brick  industry,  laid 
the  first  shale  paver  in  1884,  on  their  principal  street,  where 
it  is  still  doing  excellent  service. 

The  year  1885  witnessed  the  first  substantial  increase  in 
the  use  of  vitrified  brick,  as  during  that  year  it  was  laid  at  Growth. 
Columbus,  Zanesville  and  Steubenville,  Ohio,  and  Peoria,  111. 
Since  then  its  use  has  steadily  forged  ahead,  although  at  first 
the  progress  was  slow.  As  the  accumulated  experience  of 
brick  pavements  in  actual  use  grew  more  favorable  and  more 
voluminous  it  developed  confidence  in  the  new  material. 
Finally  the  ability  to  secure  a  strictly  first-class,  durable, 
low  maintenance  pavement  at  a  moderate  cost  appealed  so 
strongly  to  cities  of  the  second  class  and  large  towns  that 
a  regular  boom  developed  by  1895.  There  were  over  175 
plants  devoted  to  vitrified  brick,  some  of  which  had  outputs 
as  high  as  50,000,000  to  100,000,000  brick  annually  and  with 
plant  investments  as  large  as  $500,000  to  $1,000,000.  The  ex- 
panding markets  and  high  prices  that  resulted  from  the  boom 
enticed  many  small  plants  to  abandon  the  building  brick 
trade  and  enter  the  paving  brick  market,  especially  if  shale 
was  available,  as  at  first  too  many  thought  that  any  shale 
would  answer.  Many  of  those  plants  were  inadequately 
equipped  to  produce  a  good  grade  of  vitrified  brick,  while 
others  used  a  clay  from  which  it  was  impossible  to  make  a 
tough  paver.  Still  others  crowded  their  plants  and  shipped 
out  as  No.  1  pavers  anything  that  was  harder  than  a  salmon 
brick  and  not  warped  beyond  recognition. 

When  the  boom  subsided  it  had  the  wholesome  result  of 
putting  many  such  plants  out  of  business;  others  went  back 
to  their  former  legitimate  business,  while  others  were  ab- 


10  VITRIFIED    PAVING   BRICK. 

sorbed  by  the  larger  plants,  where  the  clay  had  proven  satis- 
factory. 

By  1894  vitrified  brick  had  so  favorably  impressed  the 
city  engineers  that  in  a  canvass  of  the  new  pavements  speci- 
fied that  year  in  thirty-two  leading  cities,  44  per  cent  of  the 
new  work  was  to  be  vitrified  brick,  32  per  cent  macadam,  and 
24  per  cent  asphalt-  This  was  certainly  a  very  flattering 
lead  over  its  two  great  rivals,  and  especially  over  macadam, 
its  much  cheaper  competitor. 

While  the  very  large  cities,  with  their  characteristic  con- 
servatism, were  slower  in  adopting  brick,  most  of  them  have 
since  used  it,  if  within  reasonable  freight  haulage,  for  the 
alleys,  for  the  residence  streets  and  for  the  semi-business 
streets.  A  few  efforts  have  been  made  to  lay  it  on  the  down- 
town, heavy  traffic  streets,  where  granite  or  similar  tough 
stone  is  usually  employed,  as  it  is  so  much  less  noisy  and 
smoother  than  stone  blocks.*  While  it  has  not  the  durability 
of  the  granite,  its  compensating  advantages  are  regarded  by 
many  as  sufficient  to  justify  its  occasional  renewal,  especially 
as  the  first  cost  is  usually  about  half. 

The  railroad  engineers  have  shown  the  highest  confidence 
in  the  ability  of  vitrified  brick  to  successfully  resist  the 
heaviest  traffic,  as  it  has  been  most  extensively  used  by  them 
for  paving  freight  yards  where  the  teaming  is  usually  of  the 
heaviest  nature.  They  usually  draw  specifications,  however, 
that  admit  only  the  highest  grade  of  brick  or  block. 

Misconception  DEFINITION   OF   THE   TERM   VITRIFIED   BRICK. 

of  the  Term.  There  is  frequently  a  misconception   as  to  the  definition 


*A  noteworthy  example  of  vitrified  brick  under  very  heavy 
traffic  is  the  block  on  LaSalle  street,  opposite  the  court  house, 
in  the  heart  of  Chicago,  which  was  laid  with  Purington  brick 
in  1894,  of  the  standard  or  small  size;  after  fifteen  years,' 
service,  this  pavement  is  still  in  fair  condition. 


VITRIFIED    PAVING    BRICK. 


11 


of  vitrified  brick,  as  unless  a  brick  shows  a  decidedly  glass- 
like  fracture,  some  refuse  to  call  it  vitrified,  and  even  con- 
demn brick  from  lack  of  such  glassiness  that  are  not  in- 
frequently the  toughest  and  most  durable  of  pavers  (brick 
with  a  dense  stonelike  fracture).  They  quote  Webster  to 
substantiate  their  claims,  thereby  failing  to  discriminate  be- 
tween a  popular  definition  and  a  technical  or  special  use  of 
the  term.  The  No.  1  pavers  that  are  now  on  the  market, 
whether  made  from  impure  fireclay  or  shale,  are  always  vit- 
rified, although  the  latter  are  usually  more  thoroughly  vitri- 
fied. 

To  appreciate  the  correct  use  of  the  technical  term  of 
vitrified  brick,  it  is  desirable  to  look  at  the  change  that  oc- 
curs in  paving  clays  in  passing  from  the  condition  of  a  mud 
to  a  glassy  mass.  A  plastic  clay  or  shale,  when  mixed  with 
a  proper  amount  of  water,  makes  a  mud  or  paste  that  can  be 
readily  molded,  and  it  is  tenacious  enough  to  retain  the  shape 
given  to  it  in  molding,  if  carefully  handled.  On  drying  off 
the  admixed  water  that  rendered  it  plastic,  it  shrinks  5  to  11 
per  cent  to  a  firm,  earthy  mass  that  readily  bears  handling, 
although  it  is  so  soft  as  to  be  easily  scratched  by  the  finger- 
nail, and  the  individual  particles  of  clay  can  be  easily  dis- 
tinguished- On  heating  the  dry  clay  to  a  red  heat,  or  about 
1,200  degrees  F.,  the  chemically  combined  water  is  driven  off, 
which  renders  the  clay  non-plastic,  it  again  begins  to  shrink 
and  to  grow  hard  and  strong.  As  the  heat  is  raised  above 
redness,  a  marked  increase  occurs  in  the  strength,  hardness 
and  shrinkage,  but  the  individual  particles  of  clay  are  still 
readily  recognized  and  the  mass  is  quite  porous.  When  the 
heat  is  further  raised  to  about  a  bright  cherry  heat,  or  from 
1,500  to  1,800  degrees  F.,  depending  on  the  clay,  it  shrinks 
an  additional  5  to  10  per  cent,  it  is  very  much  stronger,  much 
less  porous,  has  acquired  the  hardness  of  tempered  steel,  the 


Study  of  the 
Changes  in 
a  Clay. 


Point  of  Incipient 
Vitrification. 


12 


VITRIFIED    PAVING    BRICK. 


individual  particles  are  no  longer  recognizable,  but  the  shape 
is  perfectly  retained.  This  point,  which  is  quite  well  de- 
fined, I  have  called  the  point  of  incipient  vitrification.  From 
thence,  on  further  heating,  to  the  stage  of  a  molten  mass, 
there  is  no  longer  any  sharp  line  of  demarkation,  as  it  im- 

Viscous  Vitrifica-  perceptibly  becomes  more  and  more  vitreous,  it  slowly  and 
tion  gradually  begins  to  soften  and  if  exposed  to  pressure  (from 
the  weight  of  overlying  brick)  it  more  or  less  changes  its 
shape  ("kiln  marks").  On  still  further  raising  the  heat,  the 
clay  becomes  a  very  viscous  semi-liquid,  which,  when  chilled 
and  broken,  presents  a  glassy  to  scoriaceous  appearance. 

From  the  point  at  which  the  clay  particles  have  sufficiently 
coalesced  that  they  can  be  no  longer  recognized,  or  the  point 
of  incipient  vitrification,  to  the  point  of  viscosity,  requires 
an  increase  in  temperature  of  100  to  600  degrees  F.,  depend- 
ing on  the  clay,  and  is  usually  400  degrees  in  the  clays  suit- 
able for  paving  brick.  Midway  between  these  two  points  the 
clay  ceases  to  be  porous  and  stops  shrinking;  it  has  attained 
its  maximum  hardness  and  slightly  scratches  quartz;  it  has 
a  maximum  toughness  and  cross-breaking  strength,  if  slowly 
cooled;  the  fracture  shows  complete  coalescence  of  the  par- 
ticles, or  it  is  completely  vitrified;  and  the  shape  is  perfectly 
retained,  if  not  subject  to  pressure.  This  stage,  while  not 

Complete  Vilrifi-  sharply  defined,  I  have  called  the  point  of  complete  vitrifica- 
cation.  tion,  and  though  difficult  to  describe,  it  is  quickly  and  easily 
recognized  by  the  -trained  eye.  It  is  the  stage  that  clay 
should  be  brought  to  in  order  to  make  an  ideal  paving  brick, 
although  the  weight  of  the  overlying  brick  is  apt  to  slightly 
indent  or  "kiln  mark"  the  brick.  If  heated  higher,  there  is 
a  very  slight  loss  in  hardness,  a  much  greater  risk  of  brit- 
tleness;  there  is  a  marked  tendency  to  excessive  distortion 
and  the  fracture  is  almost  glassy;  yet  this  advanced  stage 
is  what  some  think  a  brick  should  be  brought  to  in  order  to 


VITRIFIED    PAVING    BRICK.  13 


be  called  vitrified  from  Webster's  point  of  view,*  as  it  ab- 
sorbs no  water. 

Salmon  brick,  having  only  been  exposed  to  a  red  heat, 
are  extremely  porous,  or  absorb  from  15  to  30  per  cent  of 
water;  they  are  very  soft,  or  from  2.5  to  3.0  in  hardness;  and 
they  are  very  weak,  as  they  are  in  the  initial  stage  of  shrink- 
ing, hardening  and  strengthening. 

Hard  building  brick,  having  been  raised  to  a  higher  or 
light  cherry  red  heat,  are  less  porous,  or  absorb  from  6  to  15 
per  cent  of  water;  they  are  much  harder,  or  from  4.5  to  5.5 
in  hardness;  they  are  much  stronger;  and  while  considerable 
shrinkage  occurs,  the  distinct  grains  of  the  clay  are  still 
evident. 

Fire  clay  paving  brick  usually  exhibit  a  homogeneous, 
compact,  dense  body,  in  which  the  grains  of  clay  can  no 
longer  be  discerned,  as  they  have  reached  the  stage  of  in- 
cipient vitrification;  they  are  slightly  porous,  or  absorb  from 
3  to  6  per  cent  of  moisture;  they  are  very  hard,  being  able 
to  scratch  glass  or  steel,  or  are  6.0  to  6.5  in  hardness;  and 
they  are  very  tough  and  strong.  They  are  sufficiently  dense 
and  strong  to  successfully  withstand  frost,  and  are  hard  and 
tough  enough  to  wear  well  under  moderate  traffic. 

Hard-burned  shale  pavers  usually  exhibit  a  very  dense, 
thoroughly  homogeneous,  compact  body  that  shows  complete 
vitrification;  they  are  very  slightly  porous,  or  absorb  from 
0.5  to  3  per  cent  of  moisture;  they  are  extremely  hard,  being 


*The  superficial  glassy  faces  on  brick  that  have  been  air 
checked  through  faulty  kiln  firing  should  not  be  confused  with 
the  true  fracture.  For,  on  breaking  such  a  brick,  the  body 
will  have  the  dense,  stonelike  structure  that  is  characteristic 
of  complete  vitrification,  but  which  shows  no  glassiness  what- 
ever. The  air  checked  face,  however,  looks  .decidedly  glassy, 
but  it  will  be  found  to  be  only  skin  deep,  or  only  where  the 
air  has  struck  the  crack  in  the  brick. 


14  VITRIFIED    PAVING   BRICK. 

about  able  to  scratch  quartz;  and  are  very  strong  and  tough. 
They  are  pre-eminently  adapted  for  street  paving,  if  slowly 
cooled. 

The  salmon  and  building  brick  are  too  soft,  too  porous  and 
too  weak  for  street  paving  purposes;  the  two  latter  are  both 
suitable  for  pavers,  and  are  vitrified,  but  the  important  dis- 
tinction should  be  made  that  one  is  only  incipiently  or  slight- 
ly vitrified,  while  the  other  is  completely  or  thoroughly  vitri- 
fied. 

CLAYS  EMPLOYED. 

Three  classes  of  clays  are  employed  for  the  manufacture 
of  paving  brick,  to-wit 

I.  Surface  clays,  as  the  drift,  loess  and  residual  clays. 

II.  Impure  fire  and  potters'  clays. 

III.  Shales. 

Surface  Clays.  I.     SURFACE    CLAYS. — The    surface    clays    are    seldom 

suitable  for  pavers,  although  so  very  extensively  employed 
for  building  brick.  They  are  usually  too  siliceous,  or  con- 
tain from  60  to  80  per  cent  in  silica,  and  occasionally  are  so 
very  calcarous,  or  have  from  10  to  25  per  cent  of  lime,  that  it 
is  practically  impossible  to  vitrify  a  large  percentage  with- 
out losing  their  shape.  For  the  range  in  temperature  be- 
tween the  points  of  incipient  and  viscous  vitrification  in  such 
clays  is  so  small  as  to  require  a  perfection  in  the  control  of 
the  kiln  that  renders  them  commercially  impracticable.  While 
the  earliest  pavers,  or  those  of  Charleston,  W.  Va.,  and  Bloom- 
ington,  111.,  were  made  from  such  clays,  they  were  not  vitri- 
fied, but  only  very  hard-burned  builders,  and  their  endurance 
was  due  to  the  light  traffic  of  a  small  town  rather  than  to  su- 


VITRIFIED    PAVING   BRICK.  15 


perior  quality.  In  a  few  cases*  surface  clays  have  a  com- 
position that  is  favorable  for  successfully  burning  a  large 
percentage  into  hard,  tough  brick,  but  these  are  the  exception, 
and  present  experience  does  not  indicate  that  it  will  pay  to 
add  the  mixtures  necessary  to  convert  them  into  a  good  pav- 
ing material,  as  is  done  in  Holland,  in  competition  with  the 
many  large  bodies  of  shale  that  are  favorably  constituted  for 
making  cheap  and  superior  paving  brick. 

II.     IMPURE  FIRE  AND  POTTERS'  CLAYS.— In  point  of 

history  the  impure  fire  clays*  were  next  used  for  making  pav-  ^'rc  an<*  P°tter*' 
ing  brick,  and  for  some  time  were  exclusively  employed  in  the  Clays. 
important  Upper  Ohio  district;  although  they  are  still  quite 
extensively  employed,  they  are  being  slowly  supplanted  by 
shale,  which  makes  a  somewhat  cheaper  and  usually  more 
durable  paver.  A  pure  fire  clay,  on  account  of  its  infusibility 
or  the  inability  to  vitrify  it,  is  very  unsatisfactory  for  pavers, 
as  the  brick  are  too  porous,  lack  hardness  and  strength,  and 
are  too  expensive  to  burn;  but  if  quite  impure,  it  can  be 
burned  to  incipient  vitrification,  when  the  brick  become  dense, 
hard  and  strong  and  make  a  very  fair  quality  of  pavers.  It 


*As  at  Decatur,  111.,  and  Huntington,  W.  Va.  The  Hunting- 
ton  clay  is  a  very  plastic,  tough,  safe  working  clay,  standing 
rapid  drying  and  firing,  and  is  very  fine  grained.  It  gives  the 
following  analysis  by  Mr.  Otto  Rissmann: 

Per  cent. 

Silica     57.04 

Alumina     18.26 

Sesquioxide  of  iron 6.38 

Lime     2.41 

Magnesia     1.98 

Ignition  loss   10.16 

Total  96.23 


*Also  known  as  "bastard  fire  clay"  and  pipe  clay. 


16  VITRIFIED    PAVING    BRICK. 


possess  the  great  advantage  of  being  almost  impossible  to 
overburn,  a  point  that  must  be  carefully  watched  with  shales 
or  surface  clays.  For  this  reason  the  fire  clay  brick  are  less 
porous,  or  absorb  from  2.5  to  7.0  per  cent  moisture.  They 
usually  successfully  withstand  the  frost,  in  spite  of  this  poros- 
ity, notwithstanding  the  theoretical  opinions  of  some  engin- 
eers to  the  contrary.  Brick  made  from  fire  or  potters'  clay 
usually  have  a  light  cream  or  buff  color,  from  the  small 
amount  of  iron  such  clays  generally  contain,  and  as  the  latter 
is  apt  to  be  in  the  condition  of  disseminated  grains  of  pyrite 
or  limonite,  it  gives  a  brown  or  black  speckled  appearance  to 
the  light  ground  mass.  The  fluxing  impurities  should  exceed 
5  per  cent  in  a  fine  grained  fire  clay,  or  7  per  cent  in  a  coarse 
grained  clay,  to  make  it  fusible  enough  for  paving  purposes. 
The  greater  the  amount  of  the  fluxing  impurities  the  cheaper 
it  can  be  burned,  and  the  denser,  harder  and  stronger  will  be 
the  resultant  brick,  from  the  more  thorough  cementation  of 
the  clay  particles  by  the  fluxing  action  of  these  impurities. 
The  fluxing  impurities  which  render  a  clay  fusible,  are  iron, 
lime,  magnesia  and  the  alkalies  (potash  and  soda) ;  while 
the  finer  and  the  less  dense  a  clay,  the  more  fusible  it  is,  other 
things  being  equal. 

Shales.  IIL     SHALES.* — The    material    from    which    most    of    the 

paving  brick  is  now  made,  and  which  is  usually  found  in  very 
much  larger  bodies  than  either  surface  clays  or  fire  clays,  is 
the  impure,  hard,  laminated  clay  that  is  known  as  shale  by 
the  geologists.  Though  only  recently  used  for  this  purpose, 
and  apparently  possessing  no  plasticity  as  it  lays  in  thick, 
stratified  beds,  it  is  found  to  readily  work  up  into  a  plastic 
mass  when  ground,  and  to  usually  have  the  very  impure  com- 


*Shale  is  incorrectly  called  "soapstone"  or  "soaprock"  by 
coal  miners,  from  which  it  radically  differs  in  every  respect; 
it  is  also  frequently  but  erroneously  called  slate  by  engineers, 
from  which  it  differs  but  slightly  in  origin  and  composition, 
but  slate  can  not  be  rendered  plastic  by  grinding. 


VITRIFIED    PAVING    BRICK.  17 

position  that  is  so  desirable  for  vitrified  brick.  This  very 
impure  nature  is  the  secret  of  the  success  of  shales  for  this 
purpose,  if  the  physical  properties  are  favorable.  While  there 
is  a  large  range  in  the  composition  of  paving  brick  shales, 
they  usually  range  between  the  limits  given  in  the  following 
table,  which  is  compiled  from  the  analyses  of  twenty-five 
carefully  collected  samples  of  Missouri  paving  brick  shales 
that  were  made  by  the  Missouri  Geological  Survey,  and  twen- 
ty-five brick  centers  of  the  United  States,  collected  from 
various  sources: 

COMPOSITION    OF    PAVING    BRICK    SHALES. 
(Deduced  from  fifty  reliable  sources.*) 

Minimum  Maximum     Average 
Per  cent.    Per  cent.    Per  cent. 

Silica    (SiO2)     49.0  75.0          •    56.0 

Alumina    (APO3)    11.0  25.0  22-5 

Ignition   loss    (mainly  H2O)**..       3.0  13.0  7.0 

Moisture    (H2O)    0.5  3.0  1.5 

Total  nonfluxing  constituents 87.0 

Sesquioxide  of  iron    (Fe2O3) 2.0                9-0  6.7 

Lime    (CaO)    0.2                3.5  1.2 

Magnesia    (MgO)    0.1                3.0  1.4 

Alkalies    (K2O,  Na2O) 1.0                5.5  3.7 

Total    fluxing    constituents 13-0 

Grand  total 100.0 


*There"  are  many  analyses  in  the  current  literature  that 
purport  to  be  of  paving  brick  clays  and  shales  which  differ 
greatly  from  the  above,  but  the  writer  has  found  them  to  be 
misapplied  analyses  of  burned  bricks,  kaolins,  fire  clays  or 
other  material  not  used  for  paving  brick. 

**Ignition  loss  includes  sulphur  (S),  carbonic  acid  (CO2) 
and  combined  water  (IPO),  though  mainly  the  latter. 


18  VITRIFIED    PAVING    BRICK. 


While  this  range  in  composition  is  large,  the  well-known 
paving  brick*  are  made  from  shales  that  agree  quite  closely 
with  the  average  analysis  given  above,  especially  in  the  flux- 
ing constituents,  so  that  this  will  be  a  valuable  guide  as  a 
desirable  but  by  no  means  necessary  composition  for  a  good 
paving  brick  clay.  A  specific  analysis  is  herewith  given 
(from  Orton)  of  one  of  the  best-known  shales  in  the  country 
with  regard  to  the  high  quality  of  the  brick  made  therefrom, 
or  the  Canton,  Ohio,  shale  (Royal  Brick  Co.): 

ANALYSIS   OF  CANTON    (O.)    SHALE. 
Per  cent. 

Silica    57.10 

Alumina     21.29     Nonfluxing    constituents, 

Combined    water 6.00  85.69  per  cent. 

Moisture    1.30 

Sesquioxide  of  iron 7-31 

Lime    0.29       Fluxing    constituents, 

Magnesia    1.53  13.18  per  cent. 

Alkalies  .  4.05 


Total    98.87 

Condition  of  An  imP°rtant  factor  in  the  composition  of  shales   is  the 

the  Iron  condition  of  the  iron,  which  is  always  present  in  quite  large 
quantities  in  paving  brick  shales  and  which  chemists  almost 
invariably  report  in  the  form  of  the  higher  or  sesquioxide. 
In  red  to  brown  shales  the  iron  is  largely,  if  not  entirely,  in 
the  form  of  the  higher  or  sesquioxide;  in  the  mottled  and 
variegated  shales,  both  oxides  are  usually  present;  in  the 
great  majority  of  shales,  however,  the  iron  is  the  lower  or 

*As  Moberly,  Kansas  City  and  St.  Louis,  Mo.;  Leaven- 
worth,  Kan.;  Des  Moines,  la.;  Galesburg  and  Streator,  111., 
and  Columbus,  Zanesville,  Akron  and  Canton,  Ohio. 


VITRIFIED    PAVING    BRICK.  19 


protoxide  form,  especially  when  black,  blue  or  green.  There 
is  scarcely  a  shale  bank  that  does  not  contain  "niggerheads" 
or  tough  concretions  or  round  boulders  of  impure  siderite  or 
carbonate  of  iron,  and  as  they  range  from  1  to  30  inches  in 
diameter,  the  larger  ones  have  to  be  pitched  out  to  avoid 
breaking  the  dry  pan. 

The  condition  of  the  iron  is  a  very  vital  matter  in  the  suc- 
cessful burning  of  shale,  and  more  than  one  good  shale  has 
been  condemned  from  want  of  knowledge  of  this  fact  and  the 
lack  of  ability  to  properly  control  the  burning.  For  there  is  a 
marked  difference  of  over  200  degrees  F.  in  the  fusibility,  ac- 
cording to  the  condition  of  the  iron,  as  the  protoxide  is  much 
more  fusible.  It  is  also  very  desirable  that  the  iron  be  uni- 
formly diffused  through  the  clay,  for  if  present  as  crystals, 
concretions  or  seams,  it  gives  a  mottled  or  spotted  appear- 
ance and  produces  local  vitrification,  or  in  spots.  If  the  shale 
is  thoroughly  ground,  carefully  screened  and  well  pugged, 
the  iron  usually  becomes  so  well  disseminated  as  to  cause  no 
trouble,  even  though  it  occurs  as  big  concretions  in  the  bank. 

Another  matter  that  is  frequently  misunderstood,  and 
faulty  decisions  made  in  consequence,  is  the  influence  of  lime  Influence  of 
on  clays  in  general-  If  the  lime  is  present  in  the  form  of  a  Lime. 
silicate,  as  in  feldspar,  it  is  a  very  valuable  flux,  and  the 
more  the  better;  but  if  present  in  the  form  of  carbonate  it 
will  not  make  a  strong  brick  if  in  large  amounts,  while  the 
color  will  be  cream  to  buff,  no  matter  how  much  iron*  may  be 
present,  if  the  lime  is  uniformly  diffused  through  the  clay. 
If  present  as  concretions,  pebbles  or  veinlets  and  not  finely 
ground,  the  quicklime  resulting  from  the  burning  is  liable  to 
swell  and  cause  popping  or  cracking  on  exposure  to  the  air  or 


*Iron  is  almost  invariably  the  coloring  agent  in  all  natural- 
ly colored  brick. 


20 


VITRIFIED    PAVING    BRICK. 


Fire  Clay  Mix- 
tures. 


Limited  Value 

of  Chemical 

Analysis. 


on  becoming  water-soaked.  The  failure  to  discriminate  as  to 
the  condition  of  the  lime  has  resulted  in  frequent  sweeping 
statements  condemning  lime  under  all  circumstances. 

When  shales  are  too  fusible,  fire  clay  is  sometimes  added 
to  the  extent  of  10  to  25  per  cent,  as  at  Zanesville,  O.,  and  Des 
Moines,  la.,  to  "stiffen  it,"  or  make  it  stand  up  better  in  the 
kiln,  with  satisfactory  results.  The  fire  clay  shows  in  the 
fracture  as  white  or  gray  spots  and  if  used  too  freely,  it  lowers 
the  hardness  and  toughness  of  the  brick. 

PHYSICAL  PROPERTIES  OF  CLAYS. 
The  chemical  discussion  of  clays  has  been  hastily  passed 
over,  on  which  a  volume  could  be  written  as,  no  matter  how 
carefully  a  clay  may  be  sampled  and  analyzed,  the  merits  of 
a  clay  can  never  be  decided  upon  from  only  a  chemical  analy- 
sis. It  is  of  considerable  assistance  in  forming  an  idea  about 
a  clay  and  within  certain  limits,  will  enable  one  to  condemn 
but  never  to  indorse  a  clay.  To  pass  judgment  on  a  clay  for 
any  purpose,  a  thorough  physical  examination  is  necessary, 
which  gives  the  information  how  to  work  the  clay,  the  kind 
of  the  ware  that  can  be  made  therefrom,  and  data  from  which 
the  proximate  cost  thereof  can  be  estimated.  Such  a  series 
of  physical  tests  comprise  the  determination  of  the  following: 
PHYSICAL  FACTORS  OF  CLAYS. 

1.  Plasticity. 

2.  Water  required  to  make  a  plastic  paste. 

3.  Shrinkage  in  drying. 

4.  Shrinkage  in  burning. 

5.  Speed  in  drying. 

6.  Speed  in  burning. 

7.  Temperature  of  incipient  vitrification. 

8.  Temperature  of  complete  vitrification. 

9.  Temperature  of  viscous  vitrification. 


VITRIFIED    PAVING    BRICK. 


21 


10.  Density  before  and  after  burning. 

11.  Colors  of  the  burned  ware. 

12.  Strength  of  the  burned  ware. 

All  of  these  factors  have  an  important  bearing  on  either 
the  manufacture  or  use  of  the  ware,  yet  barring  the  fusibility 
and  color,  and  then  only  imperfectly,  a  chemical  analysis  gives 
little  or  no  information  on  these  highly  important  matters. 

The  plasticity  is  pre-eminently  the  first  question  in  any  p|astjcity. 
clay,  as  on  this  properly  depends  the  ability  to  mold  the  ware. 
If  too  lean  to  be  readily  or  safely  molded,  it  requires  ad- 
mixture with  a  "fat"  or  plastic,  or  "bond"  clay,  while  if  too 
"fat"  or  plastic,  it  needs  reducing  with  sand,  "grog,"  or  a 
lean  clay.  The  plasticity  is  of  special  importance  in  paving 
brick,  as  if  too  plastic,  the  laminations,  which  have  a  weak- 
ening effect  on  the  brick,  are  excessively  developed. 

WATER  REQUIRED. — The  water  required  to  render  a 
clay  plastic  varies  considerably,  as  the  finer  the  grain  of  the 
clay,  the  greater  is  the  quantity  required.  As  paving  brick  . 
are  usually  made  by  the  stiff  mud  process,  from  14  to  18  per 
cent  is  necessary  to  secure  a  tough,  plastic  magma  that  can 
be  worked  without  excessive  power  yet  will  give  a  dense, 
close  body  that  will  have  a  moderate  air  shrinkage.  If  too 
much  water  is  used,  the  clay  can  be  worked  with  much  less 
power,  but  the  laminations  and  shrinkage  are  excessive  and 
it  is  difficult  to  handle  and  hack  the  brick  without  indenting 
them.  From  18  to  25  per  cent  is  used  in  soft  mud  brick  and 
from  5  to  10  per  cent  in  semi-dry  pressed  brick,  while  dry 
pressed  brick  only  have  the  2%  to  4  per  cent  that  all  air- 
dried  clays  possess  and  are  entirely  free  from  drying  shrink- 
age. 

SHRINKAGE. — The  shrinkage  is  a  very  important  matter      Shrinkage. 
to   the   manufacturer   and   must  be   carefully  determined   in 
order  to  know  how  much  larger  the  dies  or  molds  must  be 


22  VITRIFIED    PAVING    BRICK. 


made  to  produce  a  given  sized  brick-  It  is  made  up  of  two 
factors,  or  the  air  shrinkage  and  the  fire  shrinkage. 

AIR  SHRINKAGE.— The  air  shrinkage  is  the  reduction  in 
volume  that  takes  place  in  drying  a  plastic  clay  mass.  The 
air  shrinkage  will  be  the  greater  as  the  plasticity  increases, 
as  the  percentage  of  water  increases  and  the  finer  the  grain 
of  the  clay.  Thus  the  shrinkage  is  much  greater  in  soft  mud 
process  than  when  the  same  clay  is  worked  by  the  stiff  mud 
process  and  becomes  almost  nil  in  the  semi-dry  process  and 
is  entirely  absent  in  the  dry  process.  Coarse  and  lean  sandy 
clays  also  experience  but  a  moderate  shrinkage  in  drying. 
According  to  the  amount  of  water  used  and  the  grain  of  the 
clay,  the  air  shrinkage  usually  varies  from  4  to  8  per  cent. 

If  the  shrinkage  is  excessive  or  uniformity  of  size  is  im- 
portant, as  in  terra  cotta,  grog  or  sand  is  used  to  reduce  the 
shrinkage. 

FIRE  SHRINKAGE. — The  contraction  that  takes  place 
when  raised  above  a  red  heat,  or  the  fire  shrinkage,  varies 
considerably,  being  greater  in  fine  than  coarse  grained  clays. 
If  the  lime  and  magnesia  are  high,  the  fire  shrinkage  will  be 
slight  and  even  absent  in  a  high  lime  clay.  Usually  it  ranges 
from  5  to  10  per  cent,  which  amounts  to  10  to  20  inches  of 
"settle"  in  a  kiln,  according  to  the  clay  and  heighth  of  setting. 
The  burning  off  of  a  kiln  is  usually  determined  by  the  "settle," 
Drying  although  it  is  not  always  reliable  or  regular. 

The  speed  of  drying  determines  the  care  with  which  a  clay 
must  be  dried,  and  the  size  and  capacity  of  the  drying  cham- 
bers. Some  lean  clays  can  be  dried  in  twenty  hours  without 
checking  (small  cracks),  while  some  strong  clays  require 
three  to  five  times  as  much  time  in  order  to  dry  without 
cracking.  This  is  a  very  important  factor  to  know  in  design- 
ing a  plant  and  often  causes  heartrending  outlays  after  a 
plant  is  finished  from  having  been  overlooked-  Too  rapid 
drying  is  apt  to  affect  the  strength,  especially  with  strong  or 
very  fine  grained  clays. 


VITRIFIED    PAVING   BRICK. 


23 


The  speed  in  burning  is  a  property  that  enables  some 
clays  to  be  rapidly  heated  without  cracking,  while  others 
have  to  be  slowly  fired;  this  will  greatly  influence  the  method 
of  firing  the  kiln  and  also  determine  the  number  of  kilns  re- 
quired to  furnish  a  given  output. 

The  temperatures  of  incipient,  complete  and  viscous  vitri- 
fication are  very  important  in  all  clays,  as  it  is  necessary  to 
attain  the  first  to  develop  strength,  while  with  pavers  it  is 
not  only  of  vital  importance  to  readily  attain  the  second,  but 
there  must  be  a  wide  margin  each  side  of  the  point  of  com- 
plete vitrification  to  enable  the  kiln  burner  to  produce  xa  large 
percentage  of  No.  1  brick.  For  if  this  margin  is  small,  there 
will  be  a  heavy  loss  from  either  overburned  and  misshapen 
brick,  or  from  soft,  underburned  brick. 

The  density  of  the  burned  ware  varies  considerably,  as 
some  clays  give  a  porous,  light  body,  while  others  give  a  close, 
dense,  uniform,  stone-like  body,  which  latter  is  absolutely 
necessary  in  paving  brick. 

The  color  of  the  burned  clay  is  a  vital  matter  with  most 
clay  ware,  and  is  of  great  assistance  in  paving  brick  in  con- 
trolling the  burning,  after  once  being  familiar  with  the  colors 
of  a  given  clay  at  different  heats. 

The  strength  of  the  burned  ware  is  the  crucial  test  of  a 
paving  brick,  as  on  this  depends  its  durability.  Many  clays 
that  are  satisfactory  up  to  this  point  fail  from  the  severe  de- 
mands required  of  a  durable  paver.  In  fact,  the  majority  of 
shales  and  impure  fire  clays  can  not  be  used  for  pavers,  be- 
cause lacking  the  great  toughness  that  is  required  in  a  high 
grade  paving  brick. 

MANUFACTURE    OF   PAVING   BRICK. 

WINNING  THE  CLAY. — As  the  surface  clays  are  now 
rarely  used  for  paving  brick,  the  usual  methods  of  handling 


Burning. 


Density. 


Color. 


Strength. 


Surface  Clays. 


24 


VITRIFIED    PAVING    BRICK. 


such  clays  are  seldom  used,  or  the  pick  and  shovel,  plow  and 
scraper  or  cart,  disc  cutter  and  automatic  clay  gatherer,  ac- 
cording to  the  size  of  the  yard  and  haul.  Nor  are  paving 
brick  clays  weathered,  a  process  which  increases  the  plas- 
ticity and  homogenity,  though  at  the  expense  of  extra  han- 
dling, loss  of  time  and  the  locking  up  of  considerable  capi- 
tal; for  while  this  process  improves  all  clays,  competition 
has  now  forced  this  beneficial  measure  to  be  regarded  as  a 
luxury. 

Fire  Clays.  Tne  imPure  fire  clays  are  usually  mined  by  the  room  and 

pillar  system,  like  coal,  with  which  they  are  usually  asso- 
ciated and  much  resemble  in  their  mode  of  occurrence  and 
method  of  handling.  Like  coal,  they  are  also  preferably 
worked  by  driving  and  drawing,  or  running  entries  out  to  the 
boundary,  and  then  drawing  the  pillars  back  to  the  shaft  or 
slope. 

Shales  Tne   snales  are  usually  worked  in  open  pits,   after  strip- 

ping off  any  surface  clays,  and  are  either  worked  by  blasting, 
or  else  handled  from  the  solid  bank  into  the  car  by  a  steam 
shovel. 

Steam  Shovels.  If  the  plant  is  large  enough  to  keep  a  steam  shovel  mod- 

erately busy,  it  is  the  cheapest  and  much  the  best  way  of 
working.  For  a  much  better  mixture  of  the  different  stratas 
is  obtained,  which  differ  more  or  less  in  every  shale  bank, 
since  the  nose  of  the  shovel  rips  off  fragments  from  the  bot- 
tom to  the  top  of  the  face  every  time  it  is  loaded.  As  the 
face  is  kept  vertical,  there  is  much  less  delay  and  trouble  in 
rainy  weather  by  the  shale  not  getting  very  wet.  As  the 
depth  of  a  steam  shovel  cut  is  limited  to  about  twenty  feet, 
it  is  necessary  to  operate  the  shovel  on  a  series  of  benches 
or  terraces,  where  the  shale  exceeds  25  to  30  feet  in  thick- 
ness. 

There  is  no  limit  to  the  heighth  of  the  quarry  face  when 


VITRIFIED    PAVING    BRICK.  25 


blasting  is  employed,  and  faces  eighty  feet  high  are  worked 
at  Galesburg,  111.,  and  Des  Moines,  la.  By  putting  a  one  to 
one-and-a-half-yard  shovel  on  a  two-and-a-half-yard  machine, 
steam  shovels  are  able  to  successfully  rip  up  very  hard,  tough 
shales,  as  at  Alton  and  Galesburg,  111.,  and  Des  Moines,  la., 
though  not  without  break-downs  that  are  still  too  frequent, 
and  further  improvements  are  needed  in  strengthening  the 
weak  points  of  these  valuable  machines.  By  loosening  the 
bank  with  dynamite,  the  work  can  be  made  easier  and  much 
less  severe  on  the  steam  shovel,  but  much  of  its  economy  is 
lost  when  nitroglycerine  supplies  the  energy  instead  of  coal; 
and  if  the  points  of  the  shovel  are  kept  sharp,  they  have 
proved  their  ability  to  tear  up  very  tough  shales  without  the 
assistance  of  powder.  If  a  yard  is  making  less  than  50,000 
brick  a  day,  there  is  usually  no  economy  in  a  steam  shovel, 
as  the  shovel  crew  is  idle  about  70  per  cent  of  the  time,  and 
a  daily  output  of  about  200,000  is  necessary  to  keep  the  shovel 
constantly  at  work. 

From  the  bank  or  pit  to  the  factory,  the  clay  or  shale  is  Q,rs. 
usually  hauled  in  either  side-dumping  or  drop-bottom  cars, 
by  horse,  locomotive  or  wire  rope,  and  ingenious  devices  have 
been  introduced  for  coupling,  dumping  and  latching  automat- 
ically. Occasionally  long  belt  conveyors  are  used  to  transfer 
the  clay  from  the  pit  to  the  crushing  floor,  but  this  is  usually 
confined  to  small  plants.  For  large  plants  exhaust  the  clay 
at  the  rate  of  one-half  to  three  acres  per  year,  depending  on 
the  thickness  of  the  deposit,  as  two  cubic  yards  or  more  are 
needed  per  1,000  brick. 

CRUSHING-— Shale  is  nearly  always  crushed  in  dry  pans 
or  Chilian  mills,  with  solid  mullers  or  rolls  that  are  usually 
four  feet  diameter  and  twelve  inches  wide,  and  which  run 
within  a  revolving  pan  nine  feet  in  diameter,  with  a  grated 
bottom.  A  pair  of  such  pans  can  usually  supply  the  largest 


26  VITRIFIED    PAVING    BRICK. 


size  brick  machine,  and  they  have  proved  very  satisfactory, 
as  they  crush  from  five  to  ten  cubic  yards  of  average  shale 
per  pan  per  hour.  Rolls  and  centrifugal  disintegrators  are 
occasionally  used,  but  they  are  not  satisfactory  on  most 
shales,  which  are  usually  too  tough  to  be  cheaply  crushed 
fine  by  this  system,  although  very  efficient  on  surface  clays. 

SCREENING.— From  the  dry  pan  the  crushed  shale  should 
go  to  screens,  and  fixed,  shaking  riddles,  and  revolving  trom- 
mels are  employed.  They  all  require  the  use  of  knockers,  to 
prevent  sticking  of  the  wet  clay,  and  at  many  plants  a  boy 
is  also  needed  to  keep  the  screens  from  clogging.  The  trom- 
mels and  shaking  screens  are  more  compact  than  the  fixed 
riddle,  but  the  latter  is  simpler  to  clean  and  repair.  In  some 
of  the  older  plants  the  only  sizing  accomplished  is  by  the 
gratings  of  the  dry  pans,  which  is  regarded  as  sufficient  and 
no  screens  are  employed;  this  is  a  serious  mistake,  as  it  re- 
duces the  capacity  of  the  pan  and  results  in  very  imperfect 
screening,  from  the  wear  and  breakage  of  the  bridges  of  the 
gratings.  As  the  finer  the  clay  is  crushed  the  stronger  the 
resulting  brick,  these  coarse  particles  produce  an  inferior, 
unhomogeneous  product.  In  fact,  most  plants  are  still  faulty 
in  not  screening  fine  enough,  as  four  to  eight-mesh  screens 
are  employed,  whereas  ten  to  sixteen  meshes  per  linear  inch 
should  be  used  to  give  the  best  results. 

PUGGING. — The  crushed  and  screened  clay  or  shale  is 
next  mixed  and  worked  with  water  into  a  plastic  mass  by  the 
pug  mill,  which  is  a  long  trough  containing  a  series  of  wide 
blades  set  with  a  coarse  pitch  on  a  heavy  shaft.  This  pugging 
or  tempering  should  be  thoroughly  done  to  remove  air  in- 
closures,  secure  a  homogeneous  mixture,  and  reduce  the  lam- 
inations in  molding  to  a  minimum;  but  most  pug  mills  are  too 
short  to  properly  accomplish  this,  or  only  six  to  nine  feet  long 
(along  the  blades),  or  are  pitched  too  rapidly  and  are  the 


VITRIFIED    PAVING    BRICK. 


27 


cause  of  many  defects  in  the  brick.  They  should  be  at  least 
ten  to  twelve  feet  long,  and  have  the  blades  or  knives  90  de- 
grees apart.  Fire  clays  are  often  pugged  or  tempered  in 
"wet  pans"  or  "chasers,"  which  are  small  Chilian  mills  with 
a  solid  bottom,  while  the  mullers  have  a  narrow  tread.  The 
clay  is  both  crushed  and  tempered  into  a  homogeneous  paste 
in  this  pan,  being  kept  in  it  until  thoroughly  ground  and  uni- 
formly tempered.  The  wet  pan  yields  a  superior  product  to 
the  pug  mill,  as  it  can  be  retained  indefinitely  in  the  pan,  or 
until  thoroughly  tempered;  but  as  it  requires  a  larger  plant 
and  takes  more  labor  and  power,  it  is  not  usually  used  for 
paving  brick,  though  in  quite  universal  use  for  fire  brick, 
sewer  pipe,  terra  cotta,  etc. 

MOLDING. — Paving  brick  are  usually  made  by  the  stiff 
mud  process,  although  a  few  small  yards  still  retain  the  old- 
fashioned  soft  mud  and  repressing  system.  The  mud  process 
has  thus  far  proved  the  only  successful  method  for  securing 
a  large  percentage  of  good  pavers,  as  the  intimate  bonding 
of  the  particles  that  it  insures  adds  greatly  to  the  strength. 
Numerous  attempts  have  been  made  to  use  the  semi-dry  and 
the  dry  press  methods,  which  are  so  successfully  used  for 
building  brick,  and  thereby  eliminate  the  wet  shrinkage,  with 
its  losses,  and  the  large,  costly  drying  plants,  but  they  have 
failed  to  produce  more  than  a  small  percentage  of  good  pav- 
ers. For  in  the  dry  or  semi-dry  press  systems,  there  is  no  real 
bonding  or  cementing  between  the  clay  particles,  and  they 
merely  cohere  as  the  result  of  the  quickly-applied  pressure; 
and  unless  such  brick  are  burned  to  complete  vitrification, 
they  fail  to  give  a  solid,  strong,  non-porous  brick. 

To  show  the  strength  of  the  natural  bond  of  the  clay  par- 
ticles when  worked  by  the  mud  process,  it  was  found  in  test- 
ing about  two  hundred  samples  of  Missouri  clays  and  shales, 
that  the  dry  mud  (before  burning)  had  a  tensile  strength  of 


failure  of  Dry 
Press  Process. 


Strength  of 
Dry  Mud. 


28  VITRIFIED    PAVING    BRICK. 


50  to  300  pounds  to  the  square  inch,  averaging  about  150,  and 
the  gumbo  clays  ranged  from  300  to  400  pounds,  or  were 
much  stronger  than  the  natural  cements. 

Stiff  Mud  The  type  of  machine  used  for  the  stiff  mud  process  is  usu- 

Machines.  ally  a  continuous-working  auger  that  forces  the  tempered  clay 
or  mud  through  a  forming  die;  this  gives  a  continuous  bar  of 
stiff  clay,  which  passes  under  an  automatic  cutter  that  cuts  it 
into  the  desired  size.  As  the  bar  leaves  the  die,  it  is  usually 
sanded  to  prevent  the  bricks  from  sticking  together  in  the 
kiln.  Instead  of  an  auger  producing  a  continuous  stream  of 
clay,  reciprocating  plungers  are  sometimes  employed,  which 
give  an  intermittent  bar,  and  occasionally  steam  cylinders 
with  clay  plungers  are  used,  similar  to  sewer  pipe  presses. 
The  first  method  is  the  simplest,  and  this  style  of  machine 
has  been  developed  to  a  producing  capacity  of  12,000  bricks 
an  hour,  or  about  100,000  per  day.  Formerly  the  dies  were 
made  about  4^x2^  inches  in  size,  producing  an  end-cut 
brick,  but  of  late  9x41/4-inch  dies  are  being  used,  which  gives 
a  side-cut  brick,  and  active  discussion  is  constantly  going  on 
as  to  the  relative  merits  of  the  resulting  brick.  The  side-cut 
brick  is  the  more  shapely  and  decidedly  preferable  for  build- 
ing brick  and  for  repressing,  but  as  to  which  will  make  the 
more  solid  paving  brick — the  brick  with  fewer  laminations — 
will  have  to  be  settled  for  each  individual  clay,*  as  the  writer 
has  seen  cases  where  each  has  been  decidedly  preferable  to 
the  other.**  The  weak  point  of  the  stiff  mud  process  is  the 

*To  one  not  experienced  in  working  clays,  it  may  seem 
odd  why  a  machine  that  is  a  success  with  one  clay  is  a  failure 
with  others;  but  no  two  clays  are  alike  and  the  individuality 
is  often  so  marked  as  to  require  wide  ranges  in  the  methods 
of  working  different  clays. 

**Tests  made  on  several  Ohio  clays  by  Prof.  Orton  seem 
to  show  that  the  side-cut  are  better  than  the  end-cut,  but  the 
data  does  not  admit  of  reliable  comparison.  ("The  Clay- 
Worker,"  July,  1895). 


VITRIFIED    PAVING    BRICK. 


laminations  that  must  inevitably  result  from  pushing  a 
stream  of  clay  through  a  fixed  die.  For  the  friction  of  the 
sides  of  the  die  will  cause  differential  speeds  in  the  stream 
of  clay,  and  these  variations  must  necessarily  result  in  lam- 
inations, or  lines  of  demarkation  between  the  different  speeds 
in  the  clay  bar.  If  the  air  has  been  expelled  from  the  clay 
by  the  pug  mill,  these  lines  can  be  largely  closed  up  again 
by  a  properly  shaped  die,  and  a  first-class  brick  will  result 
in  which  the  laminations  will  be  inconspicuous  and  of  no  im- 
portance. But  if  the  air  has  not  been  expelled,  or  the  former 
and  die  are  not  properly  designed,  there  will  be  an  excessive 
number  of  concentric  lines  that  divide  a  cross-section  of  the 
brick  into  a  series  of  distinct  and  separate  shells  or  concen- 
tric cylinders  that  greatly  weaken  the  brick  for  withstanding 
blows  or  frost.  The  condition  and  character  of  the  clay  also 
greatly  influence  the  laminations,  as  the  softer  it  is  tempered 
or  the  more  plastic  it  is,  the  more  serious  is  this  trouble. 
Hence  the  clay  should  be  worked  as  stiff  as  possible  to  not 
only  make  it  dense  and  reduce  the  shrinkage,  but  also  to  re- 
duce the  laminations.  A  very  stiff  clay  needs  more  power  to 
work  it,  however,  and  if  too  stiff,  is  apt  to  break  down  the 
machine. 

REPRESSING. — In  most  factories  the  freshly  cut  brick  is 
immediately  repressed  in  special  vertical  acting  machines 
known  as  represses,  in  which  it  is  momentarily  subjected  to 
a  heavy  pressure,  usually  on  the  flat  side.  This  fills  out  the 
angles  and  edges,  making  a  much  more  shapely  as  well  as  a 
uniform  brick,  and  in  some  cases  it  probably  decreases  the 
laminations.  There  is  no  doubt  as  to  the  superior  merits  of 
a  repressed  brick  as  regards  appearance  and  uniformity  in 
size,  but  brickmakers  are  not  satisfied  as  to  the  internal  struc- 
ture being  benefited  by  breaking  the  old  bond  formed  under 
such  heavy  pressure  in  the  die  of  the  auger  machine  by  the 


End  Cut  vs. 
Side  Cut. 


Repressing. 


30 


VITRIFIED    PAVING    BRICK. 


very  differently  applied  vertical  pressure  of  the  repress.  Nor 
are  the  comparative  tests  altogether  satisfactory  that  have 
thus  far  been  made  between  repressed  and  unrepressed  brick 
made  from  the  same  clay,  which  seem  to  indicate  a  somewhat 
smaller  abrasion  loss  in  the  rattler  of  the  repressed  brick,  as 
this  is  largely,  if  not  entirely,  due  to  the  heavy  rounding  of 
the  corners  in  repressed  brick,  as  against  the  square  or 
slightly  rounded  corners  of  the  unrepressed.  For  the  ten- 
dency is  to  round  the  edges  and  corners  more  and  more, 
which  gives  a  better  footing  to  the  horse  and  makes  the  brick 
more  durable,  and  brick  are  now  rounded  with  a  three-eighths- 
inch  radius,  where  formerly  only  two-eighths  to  one-eighth 
was  used. 

DRYING.— The  stiff  mud  brick  are  hacked  or  piled  direct 
Drying,  from  the  auger  machine  or  the  repress  in  open  checker  work 
on  cars  as  high  as  they  will  bear  their  own  weight,  or  six  to 
eight  courses  high,  and  dried  in  long  tunnels  or  drying  cham- 
bers that  are  heated  either  by  direct  fires  or  by  steam  pipes, 
or  by  hot  air,  or  by  the  waste  heat  from  the  cooling  kilns- 
On  account  of  the  marked  difference  in  the  drying  properties 
of  clays,  the  selection  and  design  of  a  dryer  is  a  very  im- 
portant matter  and  the  dryer  must  be  adapted  for  the  spe- 
cific clay.  Some  clays  can  be  rapidly  dried  in  eighteen  to 
thirty  hours  without  checking  or  injury,  while  others  need 
forty-eight  to  sixty  hours  or  longer  to  avoid  cracking  to  pieces. 
This  means  a  great  difference  in  the  size,  arrangement  and 
expense  of  operating  the  drying  plant,  which  too  frequently 
is  neither  appreciated  by  the  brickmaker  nor  the  enthusiastic 
venders  of  patented  dryers,  which  generally  results  in  in- 
sufficient drying  capacity  and  a  goodly  percentage  of  un- 
sound brick. 

Burning.  BURNING. — The  burning  is  the  most  critical  part  of  the 

paving  brick  business  and  is  the  department  that  is  largely 


VITRIFIED    PAVING    BRICK.  31 


responsible  for  the  bad  brick  streets  and  is  often  the  cause 
of  the  balance  being  on  the  wrong  side  of  the  ledger  at  the 
close  of  the  year.  This  is  the  more  lamentable  as  it  is  entire- 
ly in  the  control  of  the  competent  brickmaker  if  he  has  suf- 
ficient kilns,  will  personally  supervise  this  final  department, 
and  has  the  business  sense  to  prevent  underburned,  brittle 
and  checked  brick  from  being  sent  out  as  No.  1  pavers. 
While  first-class  kiln  burners,  on  whom  largely  depends  the 
success  in  burning,  are  none  too  plentiful,  the  fruit  of  their 
work  is  easily  gauged  by  the  watchful  superintendent  who, 
by  conscientiously  classifying  into  four  grades,  should  se- 
cure the  delivery  of  60  to  80  per  cent  of  strictly  first-class 
pavers.  A  serious  fault  with  most  paving  brick  plants  in  this 
country  is  an  insufficiency  of  kilns,  as  they  are  the  most  ex- 
pensive portion  of  the  plant.  Yards  that  are  otherwise 
equipped  with  very  complete  outfits,  including  the  best  and 
latest  types  of  machinery,  are  frequently  deficient  in  kilns,  on 
which  pre-eminently  depends  the  quality  of  the  brick  and 
the  success  of  the  yard. 

The  kind  of  kiln  employed   for  burning  paving  brick  is      Down-Draft 
the   down-draft,   whether   round   or  oblong,*   as   the   up-draft      Kilns. 
type  produces  too  heavy  a  percentage  of  soft  and  overburned 
brick.    A  few  brickmakers,  who  tenaciously  cling  to  the  ideas 
they  learned  when  making  building  brick,  try  to  burn  pavers 
in  open  top  kilns;   they  succeed  in  making  a  few  No.  1  or 
strictly   hard   pavers,   and   many   No.   2   or  soft  pavers,   and 
then  try  to  find  a  customer  who  can  not  distinguish  the  in- 
ferior article. 

*The  round  kiln,  with  a  capacity  of  40,000  to  80,000  brick, 
is  a  great  favorite  in  Ohio,  the  leading  state  in  the  clay  in- 
dustry, but  the  newer,  less  conservative  western  plants  have 
mainly  adopted  the  more  convenient,  large,  rectangular  kilns, 
which  hold  from  100,000  to  300,000  brick. 


32  VITRIFIED    PAVING    BRICK. 


Continuous  Tne  continuous  kiln  has  also  been  tried  on  pavers,  but  it 

Kilns.  nas  a  discouraging  field  on  account  of  the  heavy  shrinkage 
that  complicates  the  maintenance  of  the  feeding  ports.  Im- 
provements made  at  Streator,  111.,  Catskill,  N.  Y.,  and  Erie, 
Pa.,  on  this  type  of  kiln  indicate  that  its  well-known  economy 
in  fuel  may  yet  be  utilized  for  burning  paving  brick,  with  a 
reasonable  yield  of  No.  1  brick. 

In  burning  the  brick,  which  takes  from  seven  to  ten  days, 
they  are  finally  brought  up  to  cherry  or  bright  cherry  heat, 
or  from  1,500  to  2,000  degrees  F.,  which  is  sufficient  to  vitrify 
most  shales;  but  the  impure  fire  clays  require  a  higher  tem- 
perature, or  from  1,800  to  2,300  degrees  F.*  If  shale  brick 
are  heated  too  high,  they  soften  and  "wilt  down,"  or  melt  into 
a  more  or  less  solid  mass;  yet  it  is  usually  necessary  to  bring 
them  up  to  a  heat  which  would  cause  them  to  stick  together 
if  not  prevented  by  sand  that  is  freely  sprinkled  between 
them  in  setting.  At  this  vital  temperature,  when  they  bor- 
der on  the  condition  of  a  very  viscous  fluid,  the  lower  brick 
become  "kiln  marked"  or  indented  from  the  weight  of  the 
upper  brick  forcing  the  lower  brick  slightly  into  one  another, 
and  care  is  required  to  not  allow  this  pressure  to  become  too 


*The  writer  is  well  aware  that  many  clayworkers  estimate 
their  temperatures  much  higher  than  given  above,  but  many 
careful  determinations  with  a  reliable  pyrometer  (Le  Chate- 
lier's)  have  shown  that  paving  brick  clays  almost  invariably 
vitrify  within  the  above  ranges  of  temperature.  The  clay- 
workers  have  been  frequently  misled  by  the  very  inaccurate 
determinations  of  the  early,  crude  and  erroneous  pyrometers. 
The  use  of  Orton's  or  other  good  makes  of  pyrometric  or 
seger  cones  has  placed  a  very  cheap,  simple,  reliable  means 
of  estimating  and  controlling  kiln  temperatures  within  the 
reach  of  every  one,  and  no  plant  should  attempt  to  burn  a 
kiln  without  the  use  of  cones.  They  cost  $1.00  per  100  and 
the  cones  cover  all  the  ranges  in  temperature  found  on  any 
clay  plant,  according  to  the  number  of  the  the  cone. 


VITRIFIED    PAVING    BRICK.  33 

great  by  not  setting  them  too  high.  Hence  paving  brick  are 
set  only  twenty-two  to  thirty-four  courses  high,  according  to 
the  fusibility  of  the  clay,  whereas  building  brick  are  set  thir- 
ty-five to  forty-five  courses  high.  Coal  is  used  throughout  in 
burning  pavers,  which  do  not  need  the  preliminary  or  water- 
smoking  stage  to  be  done  with  wood  or  coke,  as  in  burning 
building  brick.  Oil  and  natural  gas  have  been  used  in  a  few 
places  that  are  so  fortunate  as  to  have  these  superior  fuels; 
they  are  greatly  superior  to  coal  in  reducing  the  labor  in 
burning  and  in  producing  a  superior  quality  of  brick  from  the 
uniformity  of  the  fire,  while  the  air  checks  that  result  from 
chilling,  when  cleaning  the  grate  bars  in  coal  firing,  can  be 
entirely  prevented. 

After  the  kiln  has  been  maintained  long  enough  at  a  vitri-  Annealing. 
fying  temperature  to  heat  the  bricks  through  to  the  center, 
the  kiln  is  (or  should  be)  tightly  closed,*  and  allowed  to  cool 
very  slowly.  Slow  cooling  is  the  secret  of  toughness  and  the 
slower  the  cooling  the  tougher  the  brick.  This  annealing 
stage  is  grossly  curtailed  at  most  plants  from  insufficient 
kiln  capacity,  and  the  kiln  is  therefore  hurriedly  cooled  down 
in  three  to  five  days,  in  order  to  hurry  out  the  brick,  even 
to  removing  bricks  that  are  so  hot  as  to  set  fire  to  the  trucks. 
At  least  seven  to  ten  days  should  be  allowed  for  cooling  to 
secure  a  tough  brick,  and  those  who  desire  the  best  article 


*Prof.  Orton,  Jr.,  has  lately  advised  opening  the  fire  doors 
and  chimney  flues  while  the  brick  are  very  hot,  to  hasten  the 
cooling  until  the  top  brick  reach  a  dark  red,  before  closing  up 
tight.  This  is  a  safe  thing  to  do  in  the  hands  of  an  intelli- 
gent burner,  as  no  harm  will  result  if  the  air  is  raised  to 
nearly  the  same  temperature  as  the  brick  by  entering  the 
hot  fire  boxes  and  bags;  but  unless  carefully  watched,  this 
is  a  dangerous  risk  to  take.  ("The  Clay-Worker,"  April, 
1895). 


34 


VITRIFIED    PAVING    BRICK. 


Sorting. 


Field  of 
No.  1  Pavers. 


obtainable  can  well  afford  to  pay  the  extra  cost  of  still  slower 
cooling,  if  quality  is  the  first  consideration. 

If  the  kiln  is  properly  burned,  it  will  be  found  to  have 
from  one  to  four  courses  of  top  brick  that  are  burned  ex- 
tremely hard,  but  which  are  more  or  less  air  checked  by 
being  struck  by  the  cold  air  in  coaling  or  cleaning  the  fires. 
The  top  course  is  also  more  or  less  freely  covered  with  an 
adhering  film  of  ashes  and  dust  that  have  been  carried  over 
from  the  fire  by  the  draft.  Such  bricks  make  excellent  sewer 
or  foundation  brick,  as  they  have  a  maximum  hardness, 
crushing  strength,  a  minimum  porosity  and  are  true  and 
straight. 

Beneath  this  top  layer  of  checked  brick  to  within  two  to 
twelve  courses  of  the  bottom  are  No.  1  pavers,  or  brick  that 
should  be  perfectly  sound,  completely  vitrified,  and  have  a 
maximum  hardness  and  toughness.  Beneath  the  No.  1  pavers 
are  two  to  ten  courses  of  brick  which  have  not  received  suf- 
ficient heat  to  completely  vitrify  them,  that  are  classed  as 
No.  2  pavers  and  which  are  used  for  the  foundation  or  the 
flat  course  in  paving  and  for  building.  Beneath  the  No.  2 
pavers  are  from  one  to  six  courses  of  brick  which  have  not 
received  heat  enough  to  enable  them  to  withstand  the  frost; 
they  are  called  "builders,"  as  they  are  about  equivalent  in 
strength,  hardness  and  porosity  to  building  brick,  with  which 
they  successfully  compete.  • 

With  a  fire  clay,  it  is  possible  to  produce  90  per  cent  of 
No.  1  pavers,  as  there  is  no  risk  from  overfiring,  though  80 
per  cent  is  a  high  average.  With  shale,  one  frequently  sees 
claims  by  kiln  venders  of  the  ability  to  produce  90  per  cent 
of  No.  1  pavers,  but  such  a  very  high  percentage  is  rarely, 
if  ever,  attained,  if  carefully  graded;  80  per  cent  is  a  high 
yield  and  above  the  average,  as  most  yards  are  well  satisfied 
if  70  per  cent  are  strictly  first-class  or  No.  1  pavers. 


VITRIFIED    PAVING    BRICK. 


35 


PHYSICAL    QUALITIES    OP    PAVING    BRICK. 

COLOR. — The  color  of  paving  brick  is  no  criterion  for 
comparing  brick  made  from  different  clays,  as  clays  vary  so 
greatly  in  kind  and  degree  of  color.  Usually  the  impure  fire 
clays  give  different  shades  of  buff,  while  the  shales  give 
reds  and  browns.  For  a  given  clay,  however,  the  color  is 
a  reliable  guide  as  to  heat  it  has  received,  if  it  is  burned 
under  the  same  conditions.  The  higher  the  heat,  the  darker 
the  brick  will  be,  but  if  the  mode  of  firing  the  kiln  is  changed, 
as  from  oxidizing  to  a  reducing  action,  the  clay  will  be  made 
dark  in  consequence  of  this  reducing  action  on  the  iron,  and 
not  by  the  heat.  A  change  in  the  fuel,  as  from  oil  or  gas  to 
coal,  will  usually  result  in  a  change  in  the  color  at  the  usual 
heat  for  this  same  reason.  Uniformity  of  color  on  breaking 
the  brick  is  a  valuable  guide  in  checking  the  work  of  the 
burner,  as  a  black  center  in  a  red  brick  shows  faulty  firing, 
while  a  light  colored  center  shows  insufficient  time  in  hold- 
ing the  heat.  The  outside  color  of  the  brick  is  often  com- 
promised and  even  made  valueless  as  a  guide  by  the  sand 
that  is  employed  to  prevent  sticking  in  the  kiln,  or  by  fire 
flashing  when  using  coal  that  is  high  in  sulphur.  Some  of 
the  Ohio  valley  manufacturers  salt  glaze  their  brick,  which 
gives  a  dark  gloss  to  the  outside  that  is  very  attractive  to 
the  superficial  observer,  but  it  defeats  using  the  color  test 
unless  the  brick  is  broken.  Salt  glazing  has  been  the  cause 
of  many  soft  brick  escaping  the  inspector's  eye,  and  poor 
pavements  have  resulted  in  consequence,  but  the  practice  is 
fortunately  becoming  obsolete.  For  the  glazing  is  only  skin 
deep  and  soon  wears  off  With  some  clays,  however,  salt 
glazing  assures  a  heat  that  should  vitrify  the  body,  as  "the 
salt  will  take,"  or  the  glaze  only  occur  at  a  certain  minimum 
heat  that  assures  vitrification  with  some  clays. 

STRUCTURE. — The  structure  of  the  brick,  as  regards  its 


Uniformity. 


Salt  Glazing. 


VITRIFIED    PAVING    BRICK. 


Homogeneity. 


Variations  in 
Sizes. 


homogeneity,  density  and  vitrification,  are  determined  by  the 
fracture  on  breaking  the  brick,  as  it  is  impossible  to  deter- 
mine these  vital  questions  from  an  exterior  inspection.  The 
vitrification  should  be  complete  and  to  the  center  of  the 
brick;  it  should  be  free  from  large  spots  of  unfused  matter, 
which  latter  indicate  sand*  or  fire  clay;*  there  should  be  no 
glassy  or  spongy  spots,  which  show  imperfect  crushing  and 
mixing  of  a  more  fusible  mineral  in  the  clay.  The  structure 
should  be  uniform,  devoid  of  air  checks,  and  free  from  shakes 
or  marked  laminations,  especially  if  accompanied  by  air 
pockets.  The  edges  should  be  free  from  "ragging,"  or  ser- 
rations arising  from  obstructions  in  the  die.  "Kiln  marks" 
or  indentations  made  by  the  overlying  brick  in  burning  should 
not  be  excessive,  and  they  usually  assure  a  proper  vitrifica- 
tion. The  shape  should  be  reasonably  perfect  and  free  from 
marked  warping  or  distortion.  Slight  variations  in  the  size 
of  the  brick  may  be  due  to  the  wear  of  the  die,  or  to  varia- 
tions in  the  shrinkage  if  the  clay  is  not  uniform,  or  to  ir- 
regular burning,  or  to  irregularities  in  the  cutting  table  if 
in  length.  The  latter  is  of  no  importance  and  if  the  former 
are  moderate,  they  are  of  no  consequence  unless  due  to  un- 
derburning,  which  is  quickly  discovered  on  breaking.  If 
these  variations  do  not  interfere  with  the  close  laying  of  the 
brick,  and  the  quality  is  otherwise  satisfactory,  they  can  be 
overlooked;  but  snug,  close  laying  is  essential  to  insure  the 
durability  of  a  pavement  and  any  warping  or  variation  that 
prevents  this  should  cause  the  rejection  of  the  brick. 

HARDNESS. — The   hardness   of   a   paver   is    the   property 
that   enables   it   to   successfully   withstand   the   wear   of   the 


*The  sand  spots  are  usually  due  to  mixing  with  surface 
clays  the  shale  from  imperfect  stripping,  while  fire  clay 
seams  sometimes  occur  in  the  shales. 


VITRIFIED    PAVING    BRICK. 


37 


wagon  tire,  especially  when  the  brake  is  applied,  and  the 
slipping  of  the  horses'  hoofs.  Next  to  toughness  or  freedom 
from  chipping,  it  is  the  most  important  requisite  of  a  good 
paving  brick.  Though  its  great  importance  is  recognized  by 
engineers  and  the  inspector  is  ever  alert  for  soft  brick,  yet 
an  actual  determination  is  rarely  made  and  then  by  the  very 
imperfect  grinding  test,  which  latter  is  mainly  a  question  of 
toughness  rather  than  hardness  or  interpenetration.  An  in- 
direct estimate  of  it  is  obtained  by  the  absorption  test,  as  a 
well  vitrified  brick  is  bound  to  be  very  hard,  and  hence  a 
very  low  absorption  standard  will  insure  hard  brick.  But  it 
is  too  important  a  matter  to  be  arrived  at  indirectly,  espe- 
cially as  excellent  brick  are  found  with  3  to  5  per  cent  ab- 
sorptions. The  writer,  therefore,  suggests  the  use  of  Moh's 
scale  of  hardness  as  a  simple,  quick,  inexpensive  way  of  ar- 
riving at  the  hardness,  in  which  No.  6  is  orthoclase  feldspar 
and  No.  7  is  quartz.  Good  No.  1  shale  pavers  are  usually 
6%  in  hardness  and  are  just  able  to  scratch  tempered  steel. 
POROSITY. — The  porosity  of  a  paver  is  an  excellent  in- 
dex of  the  degree  of  vitrification,  as  if  sound  and  perfectly 
vitrified,  it  is  almost  non-porous.  The  porosity  is  measured 
by  the  amount  of  water  the  dry  brick  will  absorb  when 
soaked  in  water  for  a  given  time,  usually  24  hours.  The 
porosity  is  misapplied  by  many  engineers  as  a  critical  index 
of  the  ability  of  paving  brick  to  withstand  the  action  of  frost 
and  amusing  arbitrary  lines  are  drawn,  frequently  at  2  per 
cent,  as  to  the  maximum  porosity  that  is  permissible,  often 
requiring  less  than  many  well-known  building  stones.  This 
idea  would  be  well  founded  if  non-vitrified  brick  were  used, 
which  are  not  only  very  porous,  but  are  sometimes  so  lack- 
ing in  strength  as  to  be  unable  to  withstand  the  disintegrat- 
ing action  of  frost.  As  all  paving  brick  are  porous  to  some 
extent,  it  is  a  question  whether  the  disrupting  action  of  the 


Testing. 


Misapplied  as  a 
Frostiest. 


38  VITRIFIED    PAVING    BRICK. 

freezing  water  exceeds  the  strength  of  the  brick;  if  the  re- 
sistance of  the  brick  exceeds  the  rupturing  action  of  the 
crystallizing  water,  the  latter  will  do  the  yielding  when  it 
freezes,  and  it  is  immaterial  how  porous  it  is.  Now  vitrified 
brick,  whether  only  incipiently  vitrified  as  in  the  impure  fire 
clays,  or  completely  as  in  the  shales,  has  a  strength  that 
greatly  exceeds  the  disrupting  action  of  frost,  as  shown  by 
long  experience  and  numerous  tests;  hence,  if  the  brick  is 
vitrified  and  has  the  strength  that  usually  accompanies  vitri- 
fication, there  is  no  fear  of  frost  disintegration,  and  this  test 
should  be  used  for  its  more  restricted  but  still  high  value  as 
an  expression  of  the  degree  of  vitrification.  While  the  gen- 
erally accepted  rule  that  the  less  the  absorption  the  better 
the  brick  is  true  up  to  a  limit  of  0.5  to  1.5  per  cent,  a  brick 
should  not  be  condemned  which  gives  satisfactory  tests  in 
the  rattler,  as  is  now  done  by  some  engineers,  because  it  ab- 
Usual  sor^s  more  than  2  per  cent  of  moisture.  Most  of  the  impure 
Absorption  fire  clay  Pavers  rarely  absorb  as  little  as  2.5  per  cent,  and 
often  over  5  per  cent,  yet  they  have  been  in  successful  use 
for  over  twenty-five  years  without  being  affected  by  frost. 
The  oldest  paving  brick  in  this  country,  at  Charleston,  W. 
Va.,  which  are  still  in  fair  condition  after  thirty-five  years' 
service,  absorb  4.5  per  cent  of  water  in  twenty-four  hours, 
and  are  only  hard-burned  building  brick  made  from  a  surface 
clay.  The  Bloomington,  111.,  brick  that  wore  out  after  twenty 
years'  service  on  their  principal  street  absorbed  4.33  per 
cent,  yet  they  showed  no  traces  of  frost  disintegration,  and 
they  were  a  rough,  hand-made,  soft  mud,  building  brick  made 
from  a  poor,  calcareous,  glacial  clay.  The  Sattler  brick,  a 
hand-made,  fire  clay  block,  absorbed  5.5  per  cent,  yet  they 
successfully  withstood  the  heaviest  traffic  of  St.  Louis,  at  the 
entrance  of  the  Missouri  Pacific  Railroad  freight  yard,  for 


VITRIFIED    PAVING   BRICK. 


many  years  without  showing  the  faintest  trace  of  frost  dis- 
integration. 

The  No.  1  shale  pavers  usually  show  less  than  2  per  cent 
absorption  and  occasionally  less  than  1  per  cent;  yet  some 
of  these  almost  non-absorbent  shale  brick  are  inferior  in 
toughness  and  durability  to  the  more  porous  fire  clay  pavers. 
An  absorption  of  less  than  0.5  per  cent  is  apt  to  indicate 
brittleness,  unless  unusual  care  is  taken  in  the  annealing,  and 
the  best  shale  pavers  generally  range  from  0.75  to  2  per  cent 
on  twenty-four  hours'  soaking. 

DENSITY.— Density  is  a  desirable  factor  in  paving  brick, 

as,  other  things  being  equal,  the  denser  the  better,  from  the  Density°  ays- 
greater  quantity  of  wearing  material  in  a  given  space.  The 
density  is  obtained  by  taking  the  specific  gravity,  or  else 
the  weight  of  a  given  sized  brick,  or  else  the  weight  per 
1,000.  As  different  makers  vary  in  the  size  of  their  brick,  it 
is  dangerous  to  arrive  at  the  relative  densities  by  comparing 
the  weights  of  different  brick  per  thousand,  unless  they  are 
known  to  be  of  the  same  size.  Usually  standard  size  unre- 
pressed  brick  weigh  about  6,000  and  repressed  about  7,000 
pounds  per  thousand.  The  specific  gravity  of  a  brick  usually 
approximates  that  of  the  clay  from  which  it  is  made,  as  the 
reduction  in  size  from  shrinkage  is  about  offset  by  the  loss 
in  combined  water.  The  shales  range  from  2.15  to  2.55  and 
average  about  2.38  in  specific  gravity.  The  Coal  Measure 
fire  clays,  whether  pure  or  impure,  range  from  2.20  to  2.55 
and  average  about  2.40;  the  Mesozoic,  or  more  recent  fire 
and  potters'  clays,  are  lighter  and  range  from  1.90  to  2.22 
in  specific  gravity.  Shale  pavers  range  from  2.05  to  2.55,  and 
generally  come  within  the  limits  of  2.20  to  2.40.  Fire  clay 
pavers,  not  having  had  the  fire  shrinkage  completed,  are 
usually  lighter  or  range  from  1.95  to  2.30,  and  generally  vary 
from  2.10  to  2.25. 


40  VITRIFIED    PAVING    BRICK. 


While  a  given  clay  will  vary  in  density  according  to  the 
amount  of  burning  and  the  consequent  shrinkage,  the  poros- 
ity, in  consequence  of  not  completing  the  shrinkage,  must 
not  be  confused  with  the  specific  gravity.  The  latter  is 
primarily  the  individual  weight  of  the  molecules  and  if  two 
clays  have  been  equally  burned,  the  density  will  be  the  rela- 
tive weights  of  their  molecules.  If,  however,  the  density  has 
been  unequally  modified  by  difference  in  burning,  then  the 
porosity,  as  measured  by  the  absorption,  will  have  to  be  con- 
sidered in  arriving  at  an  accurate  idea  of  the  density,  though 
this  can  be  ignored  in  vitrified  brick  as  being  too  small  for 
practical  consideration. 

Slight  Value  as  CRUSHING    STRENGTH.— This    property    is    interesting 

a  Guide,  as  a  matter  of  general  information,  especially  as  it  shows 
that  well  vitrified  brick  are  capable  of  sustaining  the  greatest 
pressure  known,  outside  of  the  metals.*  As  a  factor  in  the 
use  of  brick  for  paving,  it  is  not  of  much  importance,  as  the 
poorest  specimens  greatly  exceed  the  heaviest  load  that  ever 
comes  upon  them  and  vitrified  brick  never  fail  by  crushing. 
Further,  the  brick  that  show  the  greatest  resistance  to 
crushing  are  the  overburned  brick,  which  are  too  brittle  to 
wear  well.  It  is  a  test  that  was  formerly  frequently  demand- 
ed by  engineers,  but  its  slight  value  and  the  expense  of  mak- 
ing the  test,  if  properly  done,  has  resulted  in  their  quite 
generally  abandoning  it.  Paving  brick  vary  greatly  in  crush- 
ing resistance,  though  the  wide  differences  that  one  sees  in 
print  are  more  usually  due  to  the  difference  in  the  mode  of 


*Tests  at  St.  Louis,  Cincinnati,  Boston,  Washington,  Buda- 
Pesth,  Berlin  and  other  places  have  repeatedly  shown  the 
crushing  strength  of  vitrified  brick  to  be  greater  than  granite. 


VITRIFIED    PAVING    BRICK. 


41 


testing,  or  else  to  the  selection  of  the  samples.*  Reliable 
samples  show  ranges  as  great  as  4,000  to  30,000  pounds  to 
the  square  inch  and  the  extreme  variations  are  found  in 
brick  made  from  shale,  which  are  conspicuous  as  making  the 
best  as  well  as  the  worst  kinds  of  pavers,  according  to  the 
clay;  they  usually  range,  however,  from  10,000  to  20,000.  The 
impure  fire  clay  pavers  show  less  variation,  or  range  from 
6,000  to  14,000  and  usually  between  8,000  to  12,000  pounds  to 
the  square  inch. 

CROSS-BREAKING  STRENGTH.— This  test,  which  is  also 
known  as  the  modulus  of  rupture,  is  of  considerably  greater 
value  than  the  crushing  test,  and  the  methods  for  making  the 
test  are  more  uniform.  This  determination  might  have  a  di- 
rect value  if  the  brick  had  a  very  poor  foundation;  but  as 
actually  used  on  a  sand  cushion,  they  rarely  break,  unless 
worn  out.  Like  the  crushing  test,  too  high  a  value  is  apt  to 
be  given  to  it  by  engineers.  It  is  preferable  to  the  crushing 
test  as  a  guide,  as  it  is  a  function  of  tensile  strength,  which 
latter  is  an  important  factor  of  the  toughness.  The  cross- 
breaking  strength  ranges  from  1,000  to  3,300,  and  usually 
amounts  to  2,000  to  3,000  pounds  per  square  inch  of  cross 
section,  as  tested  between  supports  set  six  inches  apart  and 
loaded  in  the  middle. 

TOUGHNESS. — This  is  the  most  vital  factor  in  a  paving 
brick  and  greatly  exceeds  all  the  others  in  importance.  It  is 
the  toughness  on  which  depends  whether  a  brick  will  prove 
satisfactory  in  practice,  and  which  of  two  or  more  samples 
will  be  the  more  enduring.  For  the  toughness  has  to  resist 
the  severest  of  the  destructive  agents  on  a  pavement,  or  the 


*Some  tests  given  in  the  current  literature  are  self-evi- 
dent cases  of  juggling,  as  they  have  undoubtedly  been  se- 
lected from  the  worst  samples  of  rival  brickmakers,  a  too 
common  method  of  carrying  on  commercial  warfare. 


Range  of 
Strength. 


Cross  Breaking 
Test. 


42  VITRIFIED    PAVING    BRICK. 


chipping  and  shattering  action  that  results  from  the  blows  of 
the  horses'  hoofs  and  the  bumping  and  abrasive  action  of  the 
wagon  tire. 

One  of  the  first  methods  employed  to  determine  the  tough- 
ness was  to  run  a  heavy  roller  over  the  brick  to  be  tested  by 
a  mechanical  device  that  could  be  multiplied  indefinitely  (St. 
Louis,  1880).  While  this  duplicated  the  abrasive  wear  of  the 
wagon  tire,  it  failed  to  give  the  severe  impact  action  of  the 
horses'  hoofs. 

R  ttk  ^  was  early  recognized  that  the  foundry  rattler  or  revolv- 

ing iron  barrel  offered  a  simple,  rapid,  economical  and  readily 
available  device  for  testing  both  the  resistance  to  abrasion 
and  to  impact.  Also,  that  the  rattler  test  could  be  so  con- 
ducted as  to  emphasize  either  the  impact  factor  or  the  abra- 
sive factor.  The  rattler  was  therefore  promptly  adopted  as 
the  best  method  of  determining  the  wearing  value  of  paving 
brick.  As  testing  laboratories  were  not  then  equipped  with 
them,  recourse  was  had  to  the  nearest  foundry,  where  it  is  an 
indispensible  tool  for  cleaning  castings  because  of  its  severe 
abrasive  action.  It  was  found,  however,  that  there  was  a 
marked  difference  in  the  length,  diameter  and  speed  of  foun- 
dry rattlers,  which  greatly  affected  the  results  on  the  same 
brick.  Some  engineers  also  added  scrap  iron  to  the  charge  to 
increase  the  severity  of  the  test,  while  others  substituted 
granite  blocks  and  some  added  standard  brick  to  obtain  an 
index  for  comparison.  In  the  early  years  of  the  industry  there 
was,  therefore,  a  great  range  in  the  method  of  conducting 
this  very  important  test  and  nearly  every  engineer  had  his 
own  standard.  As  a  result,  it  was  impossible  to  compare  dif- 
ferent tests  and  there  was  great  confusion.  A  brick  M  when 
tested  by  one  engineer  was  superior  to  brick  N,  while  an- 
other engineer  would  reverse  this  relative  rating  in  conse- 
quence of  the  difference  in  the  methods  by  which  the  tests 


VITRIFIED    PAVING   BRICK.  43 


were  made.  Thus  it  was  found  that  the  larger  the  rattler,  if 
run  at  the  proper  speed,  the  more  severe  was  the  impact 
action,  or  the  tendency  to  break  off  the  edges,  knock  off  the 
corners  and  even  shatter  the  brick.  If  heavy  scrap  iron  or 
granite  blocks  were  added,  the  impact  effect  was  greatly  ac- 
centuated. It  was  found  that  there  is  a  certain  speed  with  a 
given  rattler  at  which  the  impact  or  pounding  action  is  a 
maximum,  and  any  increase  or  decrease  from  this  decreases 
this  effect,  although  increase  in  speed  always  increases  the 
abrasive  or  grinding  action.  If  the  rattler  is  too  short  or  the 
shaft  runs  through  the  rattler,  the  brick  are  liable  to  bridge 
or  choke  and  thereby  greatly  decrease  the  effect  of  both  the 
impact  and  abrasion  action.  It  is  also  found  that  the  volume 
of  brick  should  bear  a  certain  ratio  of  the  volume  of  the  rat- 
tler, and  any  marked  increase  or  decrease  in  the  number  of 
brick  over  this  percentage  diminishes  the  wearing  action  of 
the  brick  on  itself  by  partially  protecting  or  muffling  if  over- 
loaded, and  not  giving  so  many  blows  if  under-loaded.  If  iron 
shot  or  other  foreign  abraders  are  employed,  it  makes  a  great 
difference  as  to  the  size  of  the  pieces  and  their  relative 
amount;  if  the  shot  is  small,  it  greatly  increases  the  abrasive 
action,  while  if  the  shot  are  large,  the  impact  factor  is  greatly 
augmented.  The  action  of  the  foreign  matter  is  also  aug- 
mented if  the  angles  and  edges  are  sharp  and  decreases  as 
these  wear  off  and  become  rounded. 

/  To  bring  about  harmony  among  the  engineers  and  to  give 
brick  manufacturers  a  definite  standard  by  which  their  brick 
would  be  tested,  the  National  Brickmakers'  Association  in 
1895  appointed  a  committee  to  thoroughly  study  the  subject 
and  deduce  therefrom  a  standard  method  of  conducting  the 
rattler  that  would  be  satisfactory  to  both  the  consumer  and 
producer  of  paving  brick.  This  committee  was  composed  of 
well-known  and  authoritative  engineers,  leading  paving  brick 


44  VITRIFIED    PAVING    BRICK. 


manufacturers  and  acknowledged  disinterested  clay  experts 
and  was  composed  of:  D.  W.  Mead  and  Willard  Beaban,  civil 
engineers;  D.  V.  Purington,  F.  B.  McAvoy  and  J.  W.  Jones, 
paving  brick  manufacturers;  and  Prof.  Edw.  Orton  and  W.  D. 
Richardson,  clay  experts.  With  them  were  associated  as 
active  participants  in  making  tests  and  taking  part  in  the  dis- 
cussions, Prof.  J.  B.  Johnson,  M.  L.  Holman  and  F.  F.  Har- 
rington, civil  engineers,  and  Prof.  H.  A.  Wheeler,  clay  expert. 

After  two  years'  work  in  testing  several  kinds  of  paving 
brick  under  a  wide  range  of  conditions,  in  which  the  size, 
speeds,  time,  volume,  percentage  and  use  of  abraders  were 
greatly  varied  in  the  rattler  tests,  the  committee  formulated 
a  method  of  testing  paving  brick  in  1897*  that  was  promptly 
adopted  by  most  municipal  engineers  and  brickmakers.  Most 
of  the  rattler  experiments  were  made  by  the  eminent  clay 
expert,  Prof.  Orton. 

Subsequently  the  engineer  of  Geneva,  N.  Y.,  Mr.  Gomer 
Jones,  suggested  a  special  rattler  in  which  the  brick  to  be 
tested  formed  the  inner  lining  and  a  charge  of  150  pounds  of 
castiron  cubes  iy2  inches  square  furnished  the  impact  and 
abrading  medium.**  While  the  Jones  method  seem  to  be 
somewhat  more  sensitive  to  variations  in  the  brick  and  to 
somewhat  more  closely  differentiate  different  brick,  its  prac- 
tical objections  have  caused  it  to  be  regarded  unfavorably. 
The  great  variations  that  usually  occur  in  good  paving  brick 
from  the  same  kiln  renders  a  delicate  refinement  unnecessary, 
especially  if  the  method  is  more  costly  and  difficult  to  make. 
What  is  wanted  is  a  simple  test  that  will  permit  a  large  num- 
ber to  be  readily  tested  with  reasonable  reliability,  so  that 

*Page  165  eleventh  annual  report  of  the  National  Brick 
Manufacturers'  Association,  1897. 

**Page  69,  thirteenth  annual  report,  1899,  ibid. 


VITRIFIED    PAVING    BRICK.  45 

the  average  value  can  be  derived  from  a  large  sample  and 
thus  eliminate  the  errors  of  sampling. 

The  work  of  Prof.  A.  V.  Talbot  at  the  Champaign,  111., 
testing  laboratory  suggested  that  the  standard  or  N.  B.  M.  A. 
rattler  test  should  be  revised,  as  he  found  that  it  did  not  suf- 
ficiently discriminate  against  underburned  or  soft  brick.  Ac- 
cordingly another  committee  was  appointed  to  reconsider  the 
rattler  test,  and  especially  to  consider  the  new  methods  of 
Jones,  Talbot  and  Orton.  This  second  committee  consisted 
of  Prof.  J.  B.  Johnson,  Gomer  Jones  and  Prof.  A.  V.  Talbot, 
civil  engineers;  D.  V.  Purington  and  J.  L.  Higby,  paving  brick 
manufacturers,  and  Prof.  Edward  Orton,  Jr.,  and  H.  A.  Wheel- 
er, clay  experts.  This  committee  modified  the  former  method 
by  introducing  a  charge  of  both  light  and  heavy  castiron 
blocks,  which,  having  a  fairly  constant  weight,  volume  and 
character,  were  found  to  clearly  bring  out  the  weakness  of 
underburned  brick.  This  was  the  defect  of  the  first  method, 
as  it  was  found  that  a  charge  of  exclusively  soft  brick  wore 
one  another  but  little  more  than  hard  brick  on  hard  brick. 
When  the  iron  shot  is  added,  however,  the  soft  brick  are  rap- 
idly worn  or  broken  and  suffer  very  severely,  as  they  would 
in  practice,  as  compared  with  hard  brick  under  the  same  con- 
ditions. The  report  of  this  committee  is  given  on  page  131, 
fourteenth  annual  report  of  the  National  Brick  Manufacturers' 
Association,  Indianapolis,  1900,  and  the  method  they  adopted 
is  subsequently  given  under  "Testing."  This  standard  or  N. 
B.  M.  A.  method  has  been  quite  generally  adopted  by  both  the 
trade  and  the  profession  throughout  the  United  States  and 
Canada,  as  it  gives  a  method  of  arriving  at  the  toughness  that 
is  just  and  acceptable  to  both  the  producer  and  consumer. 
Most  of  the  street  departments  of  our  large  cities  are  now 
equipped  with  a  standard  rattler,  as  are  also  the  public  test- 


46  VITRIFIED    PAVING    BRICK. 


ing  laboratories  and  the  yards  of  the  more  progressive  brick- 
makers. 

As  the  rattler  test  is  now  conducted,  the  loss  in  weight, 
after  being  rattled  an  hour,  varies  greatly  according  to  the 
inherent  toughness  of  the  clay,  according  to  the  care  given 
in  its  manufacture,  according  to  the  degree  to  which  it  is 
vitrified  and  finally  according  to  its  shape.  When  different 
clays  are  treated  exactly  alike,  so  as  to  exclusively  bring  out 
the  individual  toughness,  the  rattler  loss  is  found  to  range 
from  5  to  40  per  cent  and  usually  between  12  to  20  per  cent 
in  brick  that  have  proved  to  wear  well  in  practice. 

The  most  important  and  least  evident  factor  in  the  tough- 
ness of  a  paver  is  the  individuality  of  the  clay  itself  and 
which  can  only  be  determined  by  the  rattler  test  or  else  by 
use  in  the  pavement.  Shales  and  clays  that  look  to  be  simi- 
lar and  even  have  a  more  or  less  comparable  chemical  com- 
position are  found  to  vary  greatly  in  toughness  when  made 
into  pavers  under  identical  conditions  and  with  equal  care. 
So  great  is  this  difference  and  it  is  so  difficult  to  predict  this 
factor  that  no  shale  or  clay  should  be  considered  for  pavers 
until  this  extremely  important  information  has  been  obtained 
from  a  large,  working  test. 

The  care  taken  in  manufacture  to  grind  sufficiently  fine, 
to  thoroughly  screen  out  all  large  particles,  to  pug  to  a  uni- 
form and  proper  consistency,  to  so  run  the  brick  machine  as 
to  secure  a  bar  of  uniform,  unbroken,  non-ragged  structure, 
to  repress  properly,  to  handle  the  wet  brick  without  strain 
or  injury,  to  dry  equally  and  uniformly,  and  to  finally  so  fire 
the  kiln  as  to  bring  it  slowly  but  progressively  to  a  complete 
vitrifying  heat  and  to  then  gradually  cool  it  without  air-check- 
ing, everburning  or  rolling  the  brick,  all  have  great  influence 
on  the  toughness  of  a  paver.  The  variations  shown  in  testing 
different  brick  from  the  same  kiln  demonstrate  how  important 


VITRIFIED    PAVING    BRICK.  47 

the  manufacturing  factors  are  and  how  difficult  it  is  to  com- 
pletely control  them. 

The  shape  of  a  brick  or  block  will  materially  affect  the 
rattler  loss  according  as  it  is  an  unrepressed,  square  cornered 
paver  or  whether  the  sharp  edges  and  angles  have  been  re- 
moved by  repressing,  as  the  former  will  quickly  chip  off  in 
the  first  fifteen  minutes  in  the  rattler  test.  It  has  also  been 
found  that  the  ratio  of  depth  to  width  affects  the  rattler  loss, 
as  the  narrower  the  brick  the  greater  the  loss,  but  as  a  uni- 
form size  has  been  quite  generally  adopted,  this  is  not  usually 
an  important  factor. 

To  attempt  to  define  a  standard  for  the  toughness  or  rat- 
tler loss  is  unwise  and  dangerous,  as  local  conditions  as  to 
traffic  and  financial  considerations  are  liable  to  modify  any  ar- 
bitrary standard.  The  heavy  traffic  on  the  down-town  streets 
in  the  large  cities  calls  for  the  toughest  brick  obtainable, 
whereas  the  much  less  severe  travel  on  the  residence  streets 
and  alleys  in  the  same  city  will  enable  a  local  brick  that  is 
cheaper  to  make  a  good  record,  even  though  it  may  not  be 
quite  as  tough  as  a  distant  brick  made  from  a  better  clay. 
Many  small  cities  and  towns  are  able  to  secure  the  great  ad- 
vantages of  a  brick  pavement  by  using  local  pavers  that  could 
not  stand  the  expense  of  shipping  in  distant  brick,  even  though 
of  a  better  quality.  For  the  freight  is  such  a  heavy  charge 
on  long  shipments,  on  account  of  their  great  weight  (or  about 
4  tons  per  1,000),  that  it  might  render  the  cost  more  or  less 
prohibitory.  The  toughest  brick  will  unquestionably  always 
make  the  best  record  when  laid  on  the  street  and  prove  the 
most  economical  in  the  end  at  almost  any  price,  but  in  most 
cases  the  tax  payers  and  the  paving  contractors  want  the 
cheapest  brick  obtainable  and  the  toughness  or  wearing  value 
is  too  frequently  made  a  secondary  consideration,  even  when 
the  community  can  afford  the  best  brick  in  the  market. 


48  VITRIFIED    PAVING    BRICK. 


The  rattler  test  is  an  excellent  medium  for  comparing  pav- 
ing brick  with  granite  and,  while  the  latter  is  usually  very 
much  tougher  than  the  average  paver,  some  brick  have  made 
as  good  a  test  as  good  granite  in  the  same  rattler.  Granite  is 
found  to  vary  as  much  as  600  per  cent  in  the  rattler  loss, 
which  is  partly  due  to  the  difference  in  the  granites  and  part- 
ly due  to  weathering  or  incipient  decay.  For  granites  decay 
and  change  into  clay  on  prolonged  exposure  to  the  weather, 
and  while  this  requires  a  period  of  time  that  runs  into  the 
hundreds  of  years,  the  outcrops  or  exposed  parts  of  a  granite 
quarry  are  liable  to  be  considerably  softer  and  less  resistant 
than  the  material  from  greater  depths.  Brick  men  are  apt  to 
credit  granite  with  being  a  uniformly  hard  and  very  tough 
rock,  whereas,  there  are  liable  to  be  marked  variations  in  its 
paving  value.  Tests  made  in  Boston*  on  eighteen  different 
paving  brick,  in  which  granite  blocks  were  added  to  the  rat- 
tler charge,  five  of  the  brick  showed  a  smaller  loss  than  the 
granite.  Another  series  of  tests  made  at  Cornell  University** 
on  seventeen  different  makes  of  paving  brick  with  trap  blocks 
as  a  standard  for  comparison  and  rated  as  1.00,  one  shale 
paver  showed  a  loss  of  only  0.87  and  a  thoroughly  vitrified 
fire  clay  brick  a  loss  of  only  1.66;  the  loss  of  the  other  brick 
ranged  up  to  17.18  and  averaged  8.3.  As  trap  is  a  tougher 
rock  than  granite,  this  is  a  most  encouraging  exhibit  and 
augurs  well  for  the  future  of  high  grade  pavers  when  en- 
gineers insist  on  the  very  best  quality  obtainable  and  are 
willing  to  pay  for  the  enhanced  value.  For  manufacturers  can 
produce  a  much  better  brick  than  the  trade  is  usually  willing 
to  pay  for.  An  addition  of  $3  to  $5  per  1,000  to  the  present 
costs  will  permit  of  so  much  more  care  being  taken  through- 

*Engineering  News,  June  2,   1892. 
**Engineering  News,  April  18,  1895. 


VITRIFIED    PAVING    BRICK. 


49 


out  the  entire  manufacturing  process,  and  especially  in  the 
burning  and  annealing,  as  to  result  in  a  so  much  superior  ar- 
ticle as  to  make  this  additional  investment  a  measure  of  true 
economy.  For  a  brick  that  still  presents  a  smooth,  true  pave- 
ment at  the  end  of  twenty  to  thirty  years  is  very  much  cheap- 
er at  an  advance  of  $10  per  1,000  over  an  inferior  brick  that 
is  so  cobbled  and  worn  at  the  end  of  ten  years  that  it  has  to 
be  heavily  patched  if  not  renewed. 

When  square-cornered  brick  are  tested  with  those  with 
rounded  corners,  the  former  show  a  much  greater  loss,  as  the 
sharp  angles  break  off  readily.  This,  however,  is  just  what 
happens  in  practice,  and  is  a  fair  comparison  as  regards  brick 
to  brick,  but  is  unfair  as  a  test  of  the  clays,  as  they  should 
have  similar  corners  to  give  a  reliable  comparison. 

METHOD    OF    TESTING    PAVING    BRICK. 

EYE  EXAMINATION.— There  is  no  more  rapid  method,  of 
arriving  at  the  merits  of  a  paving  brick  than  by  the  trained, 
experienced  eye  when  assisted  by  the  free  use  of  a  hand  ham- 
mer. A  critical  examination  by  the  eye  and  hand  hammer 
when  combined  with  proper  experience  and  good  judgment, 
can  usually  reliably  pass  on  the  merits  of  a  brick  in  a  few 
minutes,  while  the  laboratory  tests  take  hours.  But  our  vo- 
cabulary is  too  limited  to  make  the  nice  distinctions  that  are 
possible  to  the  trained  eye  and  it  is  difficult  to  arrive  at  a 
satisfactory  numerical  evaluation.  As  in  most  expert  work,  it 
is  a  personal  decision  that  is  founded  on  good  judgment, 
training  and  experience;  and  while  it  leaves  little  to  be  de- 
sired when  backed  by  integrity  for  the  numerous  and  rapid 
decisions  of  municipal  engineering,  it  is  testimony  that  can 
be  besmirched  and  impugned  when  attacked  by  unprincipled 
self-interests.  As  definite  standards  must  be  adopted  that 
admit  of  general  use  and  comparison,  and  as  specific  figures 


Influence  of  the 
Corners. 


Necessity  of 
Tests. 


50 


VITRIFIED    PAVING    BRICK. 


are  required  that  will  permit  the  drawing  of  specifications  and 
living  up  to  same,  a  series  of  tests  have  been  devised  which 
admit  of  general  application  and  enable  definite  standards  to 
be  attained  and  lived  up  to.  The  necessity  of  such  figures  is 
so  well  recognized  that  there  are  not  only  numerous  testing 
laboratories  scattered  all  over  the  country,  but  the  engineer- 
ing departments  of  most  cities  have  laboratories  that  are  well 
equipped  to  test  brick  and  to  furnish  specific  information 
when  differences  of  opinion  arise  between  the  contractor  and 
inspector  about  the  quality  of  brick.  Usually  the  inspection 
of  the  brick  is  carried  on  at  the  work  in  the  street,  when 
about  to  be  laid,  and  the  condemned  brick  are  a  serious  ex- 
pense to  the  contractor,  who  is  often  an  innocent  sufferer; 
they  have  a  curious  way  of  disappearing  around  the  corner 
and  reappearing  laid  in  the  street.  The  proper  place  to  in- 
they  are  also  a  menace  to  the  vigilance  of  the  inspector,  as 
Inspection  they  have  a  curious  way  of  disappearing  around  the  corner 
Should  be  at  and  reappearing  laid  in  the  street.  The  proper  place  to  in- 
the  Kiln  spect  the  brick  is  at  the  kiln  as  they  are  being  loaded  out, 
where  it  can  be  much  more  rapidly,  easily  and  safely  per- 
formed and  where  there  is  no  such  strong  incentive  to  smug- 
gle condemned  brick  into  the  work.  For  even  if  the  paving 
is  done  under  a  maintenance  bond,  the  contractor  is  usually 
willing  to  take  risks  as  to  the  durability  of  questionable  brick 
that  the  cautious  engineer  would  not  entertain. 

LABORATORY  TESTS. — The  tests  that  are  made  to  de- 
termine the  complete  merits  of  a  paving  brick  are: 

I.  Density  or  specific  gravity. 

II.  Absorption  or  porosity. 

III.  Crushing  strength. 

IV.  Cross-breaking  strength. 

V.  Hardness. 

VI.  Rattler  test. 


VITRIFIED    PAVING    BRICK.  51 


The  determination  of  the  crushing  and  cross-breaking 
strengths  requires  a  large  testing  machine  of  at  least  150,000 
pounds  capacity,  which  is  expensive  and  usually  to  be  found 
in  only  well-equiped  testing  laboratories.  But  every  city  and 
brick  plant  should  have  a  balance  ($5  to  $35),  hardness  scale 
(50c),  and  rattler  ($25  to  $80),  with  which  to  make  the  other 
tests,  which  are  the  most  important  and  only  require  a  mod- 
erate outlay  if  power  is  available  for  running  the  rattler. 

While  all  these  tests  give  information  of  more  or  less 
value,  the  only  test  that  was  regarded  as  essential  and  thor- 
oughly reliable  in  arriving  at  the  wearing  value  of  a  brick  in 
a  pavement  by  the  Paving  Brick  Commission  of  the  N.  B.  M. 
A.  was  the  rattler  test. 

DENSITY.— The  density  or  specific  gravity  test  is  made  on 
half  brick  or  chips  after  they  have  been  soaked  in  water  for 
twenty-four  hours  to  fill  the  air  spaces.  A  whole  brick  should 
not  be  used,  as  the  water  can  not  usually  penetrate  into  the 
voids  in  twenty-four  hours  when  the  skin  surface  is  sound 
and  the  brick  is  vitrified.  It  is  preferable  to  take  only  a 
small  fragment  and  weigh  accurately  on  a  chemist's*  balance 
to  1  in  10,000,  rather  than  attempt  to  obtain  it  by  using  a  half 
brick  and  a  druggist's  scales,  as  usually  employed,  which  only 
weigh  to  about  1  in  300.  The  density  is  calculated  by  the 
formula: 

W 

D  =  

W'-W" 
in  which          D  =  the  specific  gravity  in  terms  of  water. 

W  =  weight  in  air  before  soaking. 
w,_       «      «     «  after 

W"=       "      "  water  after    " 

*Excellent  balances  for  this  purpose  are  sold  by  the  chem- 
ical dealers  for  $15  to  $35. 


52  VITRIFIED    PAVING    BRICK. 


ABSORPTION  TEST. — The  absorption  test  determines  the 
porosity  of  a  brick  and  the  main  value  of  this  test  is  now 
Variation  in  recognized  as  giving  the  degree  of  vitrification  rather  than  as 
Testing  a  &uide  to  its  frost-resisting  value.  For  if  the  brick  is  found 
by  the  rattler  test  to  be  tough  enough  for  a  paving  brick  it  is 
found  to  have  ample  strength  to  resist  frost  disintegration, 
immaterial  whether  the  absorption  is  high  or  low.  There  was 
formerly  much  confusion  in  the  methods  of  conducting  the 
test,  as  some  tested  the  brick  as  found,  while  others  dried 
them  out  for  variable  times  before  making  the  test.  Some 
used  whole  brick  without  even  breaking  the  less  pervious 
skin,  and  a  rough  balance,  while  others  used  chips,  which  ex- 
posed all  sides  to  a  freshly  broken  surface  and  weighed  on  a 
delicate  chemical  balance.  The  time  of  soaking  varied  con- 
siderably, which  materially  altered  the  results,  as  brick  are 
found  to  increase  in  weight  for  thirty  to  ninety  days,  though 
the  rate  is  very  slow  after  the  first  twenty-four  hours,  es- 
pecially if  hard  burned.  The  rate  of  drying  out  is  also  very 
slow  and  variable,  but  to  a  less  marked  extent  than  the  ab- 
sorption. 

It  is,  therefore,  necessary  to  adopt  arbitrary  conditions  to 
obtain  results  that  are  comparable  and  consequently  the  N. 
B.  M.  A.  method  has  been  quite  universally  accepted  as  the 
standard. 

The  specifications  for  conducting  the  absorption  test  ac- 
cording to  the  National  Brick  Manufacturers'  Association  is 
as  follows:* 

"1.  NUMBER  OF  BRICK.— The  number  of  brick  consti- 
tuting a  sample  for  an  official  test  shall  be  five. 

*Report  of  Paving  Brick  Commission  of  National  Brick 
Manufacturers'  Association,  page  83,  T.  A.  Randall  &  Co.,  In- 
dianapolis, Ind. 


VITRIFIED    PAVING    BRICK.  53 

"2.  CONDITION  OF  THE  BRICK.— The  bricks  selected 
for  conducting  this  test  shall  be  such  as  have  been  previously 
exposed  to  the  rattler  test.  If  such  are  not  available,  then 
each  whole  brick  must  be  broken  in  halves  before  the  test 
begins. 

"3.  DRYING.— The  bricks  shall  be  dried  for  forty-eight 
hours  continuously  at  a  temperature  of  230  to  250  degrees  F. 
before  the  absorption  test  begins. 

"4.  SOAKING.— The  bricks  shall  be  weighed  before  wet- 
ting and  shall  then  be  completely  immersed  for  forty-eight 
hours. 

"5.  WIPING. — After  soaking  and  before  re-weighing,  the 
bricks  must  be  wiped  till  free  from  surplus  water  and  prac- 
tically dry  on  the  surface. 

"6.  WEIGHING. — The  samples  must  be  re-weighed  at 
once.  The  scales  must  be  sensitive  to  1  gramme. 

"7.  CALCULATION  OF  RESULTS. — The  increase  in 
weight,  due  to  absorption,  shall  be  calculated  in  per  cents  of 
the  dry  weight  of  the  original  bricks." 

Or,  expressed  in  the  form  of  a  formula,  the  absorption  is 
calculated  by: 

W'-W 

"P  n -- 

W 

in  which  P  —  the  porosity. 

W  =  weight  before  soaking. 
W'=       "      after 

The  usual  absorption  of  good  shale  pavers  ranges  from 
0.8  to  2.5  per  cent,  and  if  they  absorb  less  than  0.8  per  cent, 
they  are  apt  to  be  brittle  from  over-burning.  The  usual  ab- 
sorption of  fire  clay  pavers  is  2.0  to  7.0  per  cent. 

It  is  interesting  to  note  that  after  the  N.  B.  M.  A.  commit- 
tee prepared  the  preceding  specifications  they  drew  up  the 


54 


VITRIFIED    PAVING   BRICK. 


Objections  to 
Johnson's 
Methods. 


following  resolutions,  with  which,  however,  some  engineers, 
from  lack  of  breadth  and  experience,  will  not  agree : 

"Resolved,  That,  in  the  opinion  of  this  Commission,  any 
paving  brick  which  will  satisfy  reasonable  mechanical  tests 
(rattler)  will  not  absorb  sufficient  water  to  prove  injurious 
in  service.  We  therefore  recommend  that  the  absorption  test 
be  abandoned  from  all  official  tests  as  unnecessary,  if  not 
absolutely  misleading." 

CRUSHING  TEST.— As  previously  stated,  this  test  is  now 
quite  generally  abandoned,  as  it  is  found  to  be  too  unreliable, 
especially  as  the  over-burned,  brittle  brick  usually  show  the 
greatest  strength.  When  the  test  is  made,  the  method  of  mak- 
ing it  has  such  a  very  important  influence  on  the  results  that 
the  Paving  Brick  Commission  of  the  N.  B.  M.  A.  endorsed 
Prof.  J.  B.  Johnson's  method,  which  is  as  follows: 

1.  The  crushing  test  should  be  made  on  half  bricks,  load- 
ed edgewise  or  as  they  are  laid  in  the  street.    If  the  machine 
is  unable  to  crush  a  half  brick,  the  area  may  be  reduced  by 
chipping,  keeping  the  form  as  nearly  prismatic  as  possible. 
A  machine  of  at  least  100,000  pounds  capacity  should  be  used, 
and  the  sample  should  not  be  less  than  four  square  inches  in 
cross-section. 

2.  The  upper  and  lower  surfaces  should  be  ground  to  true, 
parallel  planes,  if  possible.     If  not,  they  should  be  bedded  in 
plaster  of  paris,  while  in  the  testing  machine  and  allowed  to 
harden  ten  minutes  before  the  load  is  applied. 

3.  The  load  should  be  uniformly  increased  until  ruptured. 

4.  An  average  of  five  or  more  different  brick  shall  consti- 
tute a  standard  test. 

CROSS  -  BREAKING  STRENGTH. — The  cross  -  breaking 
strength  has  been  universally  determined  by  supporting  the 
brick  between  two  hardened  steel  knife  edges  set  six  inches 
apart,  and  applying  the  load  in  the  center  by  another  knife 


VITRIFIED    PAVING    BRICK.  55 


edge,  all  the  edges  being  rounded.    From  this  the  modulus  of 
rupture  (R)  is  determined  by  the  formula: 

3  W  1 


2  b  h* 

in  which  W  =  breaking  load  in  pounds  per  square  inch. 
1  =  length  between  supports. 
b  =  breadth  of  brick. 
h  =  height     "       " 
R  =  modulus  of  rupture  in  pounds  per  per  sq.  in. 

In  the  specifications  adopted  by  the  N.  B.  M.  A.  Commis- 
sion, it  is  stipulated  that  the  knife  edges  be  rounded  longitud- 
inally to  a  radius  of  12  inches  and  transversely  to  a  radius  of 
y8  inch,  and  that  the  average  of  ten  or  more  brick  shall  be  a 
standard  test. 

HARDNESS.  —  The  hardness  has  hitherto  been  rarely  de-  Moh's  Scale. 
termined,  and  then  by  grinding  the  brick  on  a  polishing  table, 
and  taking  the  amount  ground  off  as  a  measure  of  the  hard- 
ness. As  this  grinding  action  introduces  the  factor  of  tough- 
ness as  well  as  hardness,  it  is  a  very  unsatisfactory  test,  and 
is  now  seldom  made.  A  simple,  quick  test  that  correctly  gives 
the  hardness  is  Moh's  scale  of  hardness,  which  is  the  prin- 
cipal tool  of  the  mineralogist.  In  this  scale,  which  runs  from 
No.  1  or  talc,  which  can  be  readily  scratched  by  the  finger- 
nail, to  No.  10  or  the  diamond,  the  hardest  substance  known, 
only  Nos.  6  and  7  interest  the  tester  of  paving  brick,  as  brick 
are  too  soft  for  pavers  that  are  not  as  hard  as  6,  and  most 
pavers  are  between  6.5  and  7.0.  No.  6  is  feldspar,  or  the  white 
to  pink  mineral  that  constitutes  about  75  per  cent  of  the 
granites,  and  No.  7  is  quartz,  the  hardest  of  the  common  min- 
erals, which  is  the  colorless,  glassy  constituents  of  granites. 
In  applying  the  tests,  a  sharp  edge  or  angle  should  be  tried  Mo< 
on  a  smooth  face  of  the  object  being  tested,  and  a  firm,  strong 


56  VITRIFIED    PAVING    BRICK. 


pressure  applied.  Substances  of  equal  hardness  scratch  each 
other  with  equal  facility,  while  if  there  is  a  difference  of  0.5, 
as,  say,  6.0  and  6.5,  the  substance  that  is  6.5  will  be  barely 
scratched  by  the  6.0,  but  it  will  readily  scratch  6.0;  a  sub- 
stance that  is  7.0  in  hardness  is  not  affected  by  6.0,  while  it 
very  readily  scratches  6.0.  Practice  is  needed  to  make  fine 
distinctions,  lacking  which  the  determination  should  not  be 
attempted  closer  than  0.5,  and  the  white  dust  that  results 
from  the  scratching  should  be  rubbed  off  before  deciding 
which  is  the  harder  substance. 

RATTLER  TEST. — As  previously  stated,  the  great  con- 
fusion that  prevailed  in  the  early  days  from  the  great  differ- 
ence in  the  methods  of  conducting  this  very  important,  vital 
test  on  paving  brick  was  eliminated  by  the  painstaking  and 
elaborate  work  of  the  Paving  Brick  Commission  of  the  Nation- 
al Brick  Manufacturers'  Association,  which  was  published  in 
1897.  As  subsequent  work  showed  that  it  could  be  reason- 
ably improved  in  sensitiveness  and  made  more  reliable  in  dif- 
ferentiating between  separate  loads  of  hard  and  soft  brick, 
the  specifications  were  revised  in  1901,  which  are  herewith 
given  as  the  standard  method  of  testing  paving  brick: 

REVISED  N.  B.  M.  A.  STANDARD  METHOD  OF  CONDUCT- 
ING THE  RATTLER  TEST. 

1.  DIMENSIONS    OF    RATTLER.— The    standard    rattler 
shall  be  28  inches  in  diameter  by  20  inches  long,  measured 
inside'  the  chamber.     Other  machines  may  be  used  within  the 
limits  of  26  to  30  inches  in  diameter  and  18  to  24  inches  long, 
of  which  a  special  note  is  to  be  made  in  the  report.     Longer 
rattlers  must  be  reduced  to  proper  length  by  the  insertion 
of  an  iron  diaphragm. 

2.  CONSTRUCTION  OF  RATTLER.— The  rattler  may  be 
driven  by  trunions  at  one  or  both  ends,  or  by  rollers  beneath, 


VITRIFIED    PAVING    BRICK.  57 


but  no  shaft  shall  pass  through  the  chamber.  The  cross-sec- 
tion of  the  rattler  shall  be  a  regular  polygon  with  fourteen 
sides,  and  the  heads  shall  be  gray  castiron  that  is  not  chilled 
or  case  hardened.  The  staves  shall  preferably  be  steel  plates, 
as  castiron  peans  and  ultimately  breaks  with  a  space  of  one- 
fourth  inch  between  the  staves  for  the  escape  of  the  fine 
waste. 

3.  COMPOSITION    OF    THE    CHARGE.— A    charge    is   to 
consist  of  only  one  kind  of  brick  at  a  time  and  an  iron  abra- 
sive.    The  number  of  whole  brick  used  for  a  charge  to  ap- 
proximate 1,000  cubic  inches,  or  8  per  cent  of  the  contents  of 
the    rattler    (usually    nine    to    eleven    brick).      The    abrasive 
charge  is  to  consist  of  300  pounds  of  two  sizes  of  shot  made 
from    machine    castiron,   of  which   75   pounds    (25   per   cent) 
shall  be  the  large  size  and  225  pounds  (75  per  cent)  the  small 
size. 

4.  SIZE    OF    SHOT. — The   large    sized    shot    shall    weigh 
about  iy2  pounds  and  be  2%x2%x4%  inches  long,  with  slight- 
ly   rounded    edges.      The    small    shot    to    be    1%-inch    cubes, 
weighing  about  %  of  a  pound,  with  square  corners  and  edges. 
The  individual  shot  are  to  be  renewed  when  they  have  lost 
10  per  cent  of  their  weight. 

5.  REVOLUTIONS  OF  THE  CHARGE.— The  rattler  is  to 
make  1,800  revolutions  at  a  speed  of  29  revolutions  per  min- 
ute, with  a  permissible  range  of  one  revolution  more  or  less 
than  this  rate.    The  belt  power  should  be  sufficient  to  run  the 
rattler  at  the  same  speed,  whether  loaded  or  empty. 

6.  CONDITION  OF  THE  CHARGE.— The  brick  are  to  be 
thoroughly  dried  before  making  the  test. 

7.  CALCULATION    OF    RESULTS.— The    loss    is    to    be 
calculated  as  a  percentage  of  the  weight  of  the  dry  brick  and 
an  official  test  is  to  be  the  average  of  two  different,  complete 
charges. 


58  VITRIFIED    PAVING   BRICK. 


EVALUATION  OF  THE  TESTS.— Since  the  work  of  the 
N.  B.  M.  A.  Commission  has  shown  that  the  rattler  test  is  the 
only  safe,  reliable,  satisfactory  method  of  arriving  at  the 
wearing  value  of  paving  brick,  they  are  now  rated  and  classi- 
fied by  a  simple  comparison  of  the  rattler  results,  that  brick 
being  regarded  as  the  best  which  shows  the  least  loss  in  the 
rattler.  It  is,  of  course,  highly  essential  that  they  are  all 
tested  by  the  standard  method,  or  at  least  under  identical  con- 
ditions. 

When  the  absorption,  crushing  and  cross-breaking  tests 
were  formerly  made,  it  was  not  so  simple  to  decide  which  was 
the  best  brick,  as  the  brick  that  made  the  best  record  in  one 
test  was  not  apt  to  be  equally  as  good  in  the  other  tests.  It 
was  therefore  necessary  to  adopt  arbitrary  values  as  to  the 
relative  importance  of  the  different  tests,  and  by  formulas 
calculate  the  rating  of  a  brick.  Formulas  for  this  purpose 
were  prepared  by  Prof.  Ira  Baker  in  1891  ("Brick  Pavements," 
Indianapolis,  Ind.),  by  the  City  of  St.  Louis  in  1894  ("En- 
gineering News,"  July  26,  1894),  by  Prof.  J.  B.  Johnson  in 
1895  ("Engineering  News,"  April  18,  1895)  and  by  the  writer 
in  1895  ("Vitrified  Brick,"  Indianapolis,  Ind.,  first  edition, 
page  61).  As  these  formulae  were  seldom  used  in  practice 
and  are  now  rendered  obsolete  by  the  work  of  the  N.  B.  M. 
A.  Commission,  the  student  of  history  is  referred  to  the  above 
originals  for  the  details  of  same. 

UNIFORMITY  OF  RESULTS.— In  testing  brick  at  least 
Variations  in  five  specimens  of  each  lot  or  kind  should  be  tested,  and  prefer- 
Paving  Brick,  ^jy  ten>  an(j  tne  results  averaged.  If  the  samples  are  taken 
from  different  kiln  runs  and  made  at  different  times,  it  adds 
greatly  to  their  reliability  if  the  individual  tests  closely  agree ; 
but  if  the  results  vary  greatly,  such  a  clay  is  open  to  sus- 
picion until  careful  resampling  and  testing  shows  whether  it 
is  due  to  careless  sorting  or  to  manufacture.  The  best  brick 


VITRIFIED    PAVING    BRICK.  59 

vary  from  15  to  30  per  cent  in  the  tests,  while  inferior  brick 
exceed  50  per  cent,  and  this  range  is  a  very  valuable  check 
on  the  care  in  making  the  brick,  and  on  the  sorting  in  load- 
ing. To  illustrate  the  variations  that  usually  occur  in  paving 
brick,  the  following  table  gives  results  obtained  by  the  Civil 
Engineering  Department  of  the  University  of  Illinois  from 
samples  selected  from  twenty-four  paving  brick  plants  in  Illi- 
nois, Indiana,  Ohio,  Missouri  and  Kansas  by  the  Illinois  Geo- 
logical Survey: 


ill 

00  00  00  OO 

X  X  X  X 

10  «O  10  10 

d  os  os  os 
^  X  x  X 

S 

******  • 

OlOlO 

i^ioio 

20x9.5x6-7 

21x9.5x8.5 
21x10x8 

24x11x8.5 
23x10x8 
22.5x10x8 
23-5x10.5x8 

i 

10 

Y, 
10 

OS  00  IO  10 
^IOIO»0 

21x10x5.5 
21x10x8 

sil 

OODfi 

3600  to  4870 
3000  to  6420 
2670  to  4280 

55 

5555 

1440  to  5000 

'iosoto'raoo' 

4740  to  5900 

O 

HH 

06  8 

!l| 

1| 

1240  to  1960 
2080  to  3100 
1200  to  1680 

5555 

§06  •*  S 
OV  JO  'M 

0  0  0  O 

IQ  O  CD  O 

0 

O  O  O  0 
«a«a4A4-> 

1918  to  2844 

f>*     C 

EH   , 

O  r-  it-  IN 

«<M  O  US 

COiMi-HO 

COG^CilC 

10 

Or-HOTfl 

0 

|i 

DOO 

=222 

o222 

O  O  O  O 

«  d  d  d 

oS2S 

5 

(M 

o555 
4^ 

O 

O 

d 

.     o 

?0I     ^ 

•<!  PS     :  — 

«»« 

**** 

ss 

as2S 

6888 

Tfi  SOO3  JO 

SOS^iiO 

§1 

2fe,3           Q  >• 

Ss  is 

*-*i- 

in 

ssss 

S83SS 

« 

SSSS 

d 

ll 

3i»   i» 

ssi  Stf 

^2» 

ss" 

•  os 

8SSS 

«88a 

s 

IQ 

00 

W  -e 

1  «     s£ 

00—  I'M  ^H 

t-  03  00  OS 

•M 

Addas' 

OS 

d  TtJ  (M*  TlJ 

10 

5  -s 

•<    o       ^P5 

>  D 

:  :  :  : 

:  : 

:  :  :  : 

§1 

FH      - 

«g 

fi  " 

<<  « 
«  pq 
0  fe 

0 

a 

;^i 

s«;.s 

IB^aO 

Soft  Burned 
Alley  
No.  1  paver 
Overburned 

£  • 

1; 

Soft  
Alley  
No.  1  paver 
Overburned 

ill 

•      &  3 
Jfe"1^ 

iiil 

Soft  
Alley  
No.  1  paver 
Overburned 

il 

:3 
pq  :fc 

V) 

H 

M 

s 

5 

:  : 

fi 

fc 

:  ;  :  : 

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:      : 

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;   !   ;   ; 

'.'.'.'. 

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M"  " 

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Albion,  111  . 

M*    "    " 

a 
or:  : 

Atchison,  E 

Barr  Olay  O 

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fl:  :  : 

C 
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5 

Ooffeyville, 

II 


05050401 

X  X  K  X 

00010 


04OSOS004U3 


(N  0^1  ff«  (N  <N  (N 

dddddb 


3i 

01000 

SSBS 


lOx8.6 
x10x8 


•«o-*t- 
•000 

iiii 

:^<NlO 


^222 


22 


2222 


222 


22 


^N0i~ 


t-T  OiO5 


o222 


»oo 
*i  r-i 

22 


o222 


222255 

•*XO  •*  Oi  t^ 

us  co  d  d  •*'  so 


2^2 


U500 

0  O  O 


05100 

odd 


uaa    • 


xo 

ss 


<N  •*  «  «0  t-  04 

X'  >O  i-H  5O  r-l  i-H 


(NO 

10  ^ 


t-(N05X 


No.  1  paver 
No.  2  paver 


do 


ill 

iS 

3oS 
<«3!z;o 


rdsvi 


PQ 
u> 
c.  . 

>" 

£ 

2.  - 
f" 

X 


fc£  ,  oo 

il 


x10x8 
10x8.5 


23-5x10x9 
23.5x10x9 
x9.75x8.5 


£«D! 
H  HS 

UCG£ 


00  to 
00  to 


t-Oft!N01 


Si 


22 


n 

<     D 


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t>oo' 


«*=• 


IOCOOJ  1C 


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I 


VITRIFIED    PAVING    BRICK.  63 

USES    OF  VITRIFIED  BRICK. 

In  addition  to  having  outdistanced  its  rivals  as  the  most 
popular  material  for  a  good  street  pavement,  vitrified  brick  is 
also  very  extensively  used  for  sewers,  buildings,  sidewalks, 
foundations  and  chemical  purposes. 

SEWERS. — On  account  of  its  exceptional  hardness,  vitri- 
fied brick  is  so  greatly  superior  to  common  brick  for  sewer  Uses  °f 
construction  that  it  has  very  largely  replaced  it,  at  least  for  Vitrified  Brick. 
facing  the  sewer.  Its  low  porosity  and  high  strength  also  add 
additional  merit  for  this  rapidly  growing  use  of  vitrified  brick. 
The  severe  scouring  action  of  the  sand  that  is  swept  through 
the  sewers  by  storm  waters,  which  is  so  destructive  when 
common  brick  is  used  (especially  where  the  grades  are  con- 
siderable, as  in  hilly  cities)  scarcely  affects  vitrified  brick  and 
very  greatly  prolongs  the  life  of  the  lining  of  the  sewer,  if 
it  does  not  entirely  remove  the  need  of  relining. 

When  our  cities  are  paved  with  hard  pavements  and  the 
use  of  macadam  is  abandoned,  the  cleaning  of  our  streets  will 
be  revolutionized  if  the  sewers  are  lined  with  vitrified  brick. 
For  then  it  will  be  safe  to  use  the  hydraulic  system  for  clean- 
ing the  streets,  which  the  present  soft  lining  of  our  sewers — 
at  least  the  old,  main  or  trunk  sewers — usually  prohibits,  as 
the  scour  would  destroy  them.  Under  the  hydraulic  system, 
the  cleaning  would  not  only  be  much  more  thorough,  efficient 
and  rapid,  but  also  much  cheaper  and  entirely  free  from  the 
unhealthy  dust.  A  small  hose  crew,  with  the  power  furnished 
by  coal  at  the  city  water  works,  would  replace  our  present 
large  gangs  of  men,  sweeping  machines  and  dirt  carts.  The 
heavier  demand  for  water  that  this  flushing  system  of  clean- 
ing would  create  would  naturally  require  it  to  be  done  at 
night  when  the  consumption  is  small,  although  this  is  the 
only  time  that  the  cleaning  of  the  streets  should  be  tolerated. 

BUILDINGS.— The   use   of   vitrified   brick   for   building  is 


64  VITRIFIED    PAVING    BRICK. 


growing  steadily,  as  architects  have  found  that  it  does  not 
fade  and  that  it  remains  clean.  Soot  and  dirt  do  not  find 
ready  lodgement  as  on  stone,  unglazed  terra  cotta  and  front 
brick,  while  every  rain  storm  tends  to  wash  it  clean.  In  the 
first  invasion  of  the  building  brick  trade  by  vitrified  brick, 
the  efforts  were  mainly  directed  at  working  off  stock  that  was 
too  brittle  from  over-burning,  or  too  badly  warped,  or  too 
soft  for  paving.  By  "rock-facing"*  the  over-burned,  warped 
and  brittle  brick,  surprisingly  pleasing  effects  can  be  ob- 
tained when  laid  in  the  wall.  Some  of  the  more  aggressive 
architects  were  so  pleased  with  the  picturesque  effects  that 
could  be  obtained  when  the  ordinary  paving  brick  is  used 
with  skill,  that  it  has  become  quite  popular  and  is  being  freely 
used  by  many  of  the  leading  lights  of  the  profession,  although 
often  under  a  special  trade  name. 

FOUNDATIONS. — The  low  absorption  and  high  crushing 
strength  of  vitrified  brick  make  it  an  admirable  material  for 
foundations,  especially  in  wet  ground,  or  for  bridge  piers  or 
for  very  high  buildings.  The  heavy  pressures  that  have  to  be 
sustained  in  the  construction  of  the  modern  tall  office  build- 
ings is  especially  favorable  for  vitrified  brick,  as  it  is  not  only 
stronger  and  very  much  cheaper  than  granite,  but  it  effect- 
ually keeps  out  dampness. 

SIDEWALKS. — One  of  the  earliest  applications  of  vitrified 
brick  was  for  sidewalks,  as  it  is  so  very  much  more  durable 
than  the  so-called  "sidewalk"  brick  that  are  obtained  from  a 
building  brick  kiln.  The  top  course  or  two  of  pavers  in  a 
kiln  are  especially  adapted  for  sidewalk  use,  as  they  are  per- 
fect in  shape,  they  are  free  from  kiln  marks  and  thoroughly 


*In  rock-facing,  one  face  of  the  brick  is  chipped  or  dressed 
into  a  rough,  irregular  face  with  a  hammer  and  chisel,  which 
gives  it  an  attractive,  unique  appearance. 


VITRIFIED    PAVING    BRICK.  65 


vitrified,  while  the  air  checks  are  not  apt  to  be  objectionable 
for  this  purpose.  Their  great  strength  enables  them  to  be 
laid  flat  without  danger  of  breaking,  which  happens  so  fre- 
quently with  common  brick. 

CHEMICAL  PURPOSES.— For  lining  vats  and  tanks  and 
for  constructive  work  about  chemical  factories,  vitrified  brick 
is  very  valuable,  as  it  is  not  attacked  by  acids  or  other  pow- 
erful chemicals  that  usually  destroy  common  brick  and  other 
building  material. 

STREET  PAVING.— The  great  field  for  vitrified  brick,  in 
which  it  has  earned  a  well-deserved  popularity,  is  for  street 
pavements  in  our  cities,  towns  and  important  county  turn- 
pikes. For  it  is  capable  of  meeting  the  most  exacting  de- 
mands of  our  largest  cities,  while  its  cost  can  be  brought 
down  within  the  reach  of  the  small  town  and  the  prosperous 
farming  community.  This  marked  elasticity  in  the  cost  of 
securing  a  good  brick  pavement  to  meet  local  conditions  has 
resulted  in  its  being  the  most  popular  paving  material  to- 
day in  the  greater  part  of  our  country,  or  that  great  area  that 
extends  from  the  Hudson  River  to  the  Rocky  Mountains,  and 
from  Canada  to  Mexico.  Within  that  enormous  territory  there 
are  over  one  hundred  and  fifty  paving  brick  factories  that 
have  suitable  clays  (although  some  are  much  better  than 
others),  so  that  freight  rates  in  most  cases  are  not  restrictive. 
To  the  east  of  the  Hudson  River  suitable  clays  are  scarce,  so 
that  the  freight  rates  are  nearly,  if  not,  prohibitive  in  ship- 
ping in  high  grade  brick  from  the  West,  while  local  macadam 
is  apt  to  be  cheap  and  of  excellent  quality.  To  the  west  of 
the  Rocky  Mountains  the  paucity  of  the  population  and  the 
prohibitive  freight  rates  bar  out  vitrified  brick,  except  in  a 
few  local  instances  and  the  Pacific  Coast  cities. 

OTHER  PAVING  MATERIALS.— The  principal  competi- 
tors of  vitrified  brick  for  street  and  alley  paving  are: 


66  VITRIFIED    PAVING    BRICK. 

Macadam  or  broken  stone,  including  telford,  novacutile,  etc. 

Wood  blocks,  including  sawed  and  round,  prepared  and  un- 
prepared. 

Asphalt  and  bitulithic  pavements. 

Granitoid  (for  alleys)  or  concrete. 

Cobble  stones,  or  small  boulders  or  rounded  stones. 

Stone  blocks,  or  dressed,  rectangular  blocks  of  hard  stone, 
as  granite,  trap,  sandstone,  etc. 

Macadam  MACADAM. — The    macadamized    road    is    a    very    elastic 

term  that  covers  the  rural  road  on  which  there  may  be  only 
four  inches  of  broken  stone  to  the  high  grade  telford  that  has 
a  9-inch  foundation  of  rubble  or  coarse  rock,  a  4  to  6-inch  sub- 
base  of  smaller  rock,  a  2  to  4-inch  cover  of  2-inch  rock  and  a 
2-inch  top  dressing  of  y2  to  1  inch  rock  or  gravel  with  a  suit- 
able binder.  There  is  consequently  a  great  range  in  the  cost, 
although  in  almost  all  cases  they  are  the  cheapest  of  hard 
pavements.  Whether  well  built  or  cheaply  built,  they  all  have 
the  common  weakness  of  requiring  incessant  patching  or  re- 
pairing and  they  are  dusty  in  dry  weather  and  muddy  in  wet 
weather  unless  maintained  in  an  ideal  condition  that  is  sel- 
dom seen.  When  frequently  and  lightly  sprinkled,  they  make 
ideal  park  roads  if  only  light  driving  is  permitted  and  they 
are  properly  drained.  Too  frequently,  where  the  sprinkling  is 
done  by  contract,  they  are  over-deluged  and  rendered  muddy 
as  well  as  injured  to  reduce  the  number  of  trips,  yet  if  it  is 
hot  or  windy,  they  are  dusty  again  before  the  next  trip  of  the 
water  wagon. 

Under  heavy  traffic  the  surface  wears  away  rapidly,  while 
ruts  and  chuckholes  increase  with  remarkable  rapidity.  This 
constant  resurfacing  and  filling  up  of  the  ruts  calls  for  a  lib- 
eral maintenance  outlay,  especially  as  the  worn  out  (crushed) 
old  surface  has  to  be  scraped  off  before  it  is  renewed  with  an- 
other top  dressing.  To  show  how  heavy  the  wear  is  on  a  ma- 


VITRIFIED    PAVING    BRICK.  67 


cadamized  street  that  was  used  moderately,  it  was  found  on 
one  of  the  side  streets  of  St.  Louis  where  a  hard  limestone 
macadam  was  employed  that  the  accumulation  of  the  broken 
stone  hauled  on  it  for  repairs  would  have  filled  the  street  to 
above  the  second  floors  of  the  houses  if  the  worn  out  surfaces 
had  not  been  partially  blown  away  as  dust,  partially  washed 
down  the  sewers  as  an  impalpable  mud  and  partly  hauled  off 
as  scrapings. 

On  account  of  their  low  cost,  the  macadam  road  still  con- 
stitutes the  largest  mileage  in  this  country,  as  it  is  usually 
the  first  step  forward  from  the  dirt  road,  which  latter  in  Amer- 
ica is  usually  a  right  of  way  that  is  generally  impassable  for 
two  to  four  months  in  the  winter  and  early  spring  from  the 
heavy  mud  and  is  quite  frequently  almost  prohibitive  in  the 
summer  from  the  excessive  dust. 

As  the  wealth  of  a  community  increases  and  especially 
when  it  appreciates  that  the  best  is  the  cheapest,  the  macad- 
am road  is  nearly  always  replaced  by  a  brick  pavement. 

The  rapid  growth  in  the  use  of  the  automobile  has  been 
very  severe  on  macadamized  roads,  as  their  high  speeds  are 
very  trying  on  the  binder,  loosening  it  and  starting  the  de- 
struction of  the  pavement.  This  has  been  partially  mitigated 
by  oiling  the  roads  with  petroleum  residuum,  which  also 
greatly  alleviates  the  dust  nuisance,  but  the  oil  is  trying  on 
the  rubber  tires. 

WOOD  PAVEMENTS.— Almost  every  city  in  this  country      Wood  Block 
has  tried  the  wood  block — both  round  and  sawed — been  high-      Pavements. 
ly  pleased  with  it  for  a  while,  but  after  laying  perhaps  quite  a 
large    mileage,    have   later    almost    invariably    condemned    it. 
Later  on,  under  a  new  name  or  material  or  different  prepara- 
tion, the  wood  block  has  been  laid  again  and  subsequently  se- 
verely condemned  when  the  repair  period  arrived.     This  ex- 
perience has  been  frequently  repeated  in  many  of  our  large 


68  VITRIFIED    PAVING    BRICK. 


cities.  Formerly  the  wood  pavement  was  usually  cheap  and 
for  the  first  two  to  four  years  of  its  life,  if  well  laid,  it  made 
a  fair  pavement  and  it  is  always  noiseless.  But  when  wear 
and  decay  set  in  it  is  so  difficult  to  keep  in  repair  that  it  is 
usually  abandoned  as  a  hopeless,  rough,  soggy  street  until 
forced  to  replace  it  with  a  more  durable  pavement.  While 
the  unprepared  wood  lasts  three  to  seven  years,  according  to 
the  wood  and  the  thoroughness  of  the  inspection,  when  it  is 
properly  creosoted  its  life  can  be  lengthened  to  five  to  eight 
to  ten  years,  according  to  the  travel.  Since  wood  has  so 
greatly  advanced  in  price,  the  former  attractive  cheapness  of 
the  wood  pavement  has  largely,  if  not  entirely,  disappeared 
and  it  is  now  rarely  laid  without  being  creosoted  or  other- 
wise protected  from  decay. 

As  the  density  of  the  traffic  increases  in  our  large  cities, 
the  noise  becomes  more  and  more  serious  and  around  such 
buildings  as  court  houses,  schools  and  churches  the  elimina- 
tion of  the  noise  is  sometimes  so  important  that  wood  blocks 
are  again  being  used  in  spite  of  the  fact  that  they  have  to 
be  renewed  every  five  to  seven  years.  For  it  is  the  only  hard 
pavement  that  is  noiseless  and  clean.  In  London,  England, 
where  the  traffic  density  is  greatly  in  excess  of  any  other  city 
in  the  world,  wood  pavements  have  been  regarded  as  a  neces- 
sity for  many  years,  as  the  roar  of  the  wagon  traffic  would 
otherwise  be  unbearable.  They  employ  a  very  hard  imported 
oW  wood,  which  is  sawed  to  make  a  close  fitting  pavement,  and 

its  life  is  usually  five  to  six  years. 

Asphalt  and  ASPHALT     AND     BITULITHIC.— An     asphalt     pavement 

Bitulithic  makes  an  ideal  sanitary  street,  as  the  surface  is  an  unbroken 
sheet  about  two  inches  thick  of  impervious  asphaltic  mixture 
and  for  this  reason  asphalt  has  been  largely  used  in  the  dense 
tenement  districts  of  New  York  City.  Because  it  presents  an 
unbroken  surface,  its  tractive  resistance  is  very  low  during 


VITRIFIED    PAVING    BRICK.  69 

the  cool  weather,  but  in  very  hot  weather  it  softens  more  or 
less  and  is  not  so  satisfactory.  It  gives  a  very  poor  footing 
to  the  horses  and  when  wet  it  becomes  so  slippery  as  to  be 
almost  prohibitive  for  heavy  teaming. 

It  is  an  expensive  pavement,  as  it  requires  a  6-inch  con- 
crete foundation  and  the  asphaltic  sheet  is  a  complex  of  pre- 
dominant limestone  dust  (as  a  filler),  sand,  asphalt  and  pe- 
troleum residuum  that  requires  special  skill  to  properly  pro- 
portion and  lay.  If  overheated,  the  asphalt  is  injured  and  if 
insufficiently  heated  it  does  not  stand  the  weather,  while  the 
asphalt  itself  is  an  uncertain  compound  that  not  only  varies 
with  every  deposit,  but  often  in  the  same  deposit.  To  prop- 
erly lay  a  first-class  asphalt  pavement  that  will  not  crack  in 
winter  nor  soften  in  hot  weather  is  an  art  that  no  city  street 
department,  with  its  political  complications,  can  hope  to  do,  so 
that  the  work  is  usually  done  on  contract  by  specialists  who 
ship  their  crews  from  city  to  city. 

As  it  is  difficult  in  such  an  uncertain  complex  to  secure  a 
uniform  mixture,  asphalt  pavements  usually  wear  rapidly  into 
holes  and  bad  spots  that  should  be  looked  after  every  month 
or  two,  but  these  can  be  easily  cut  out  and  the  surface  re- 
newed by  a  skillful  crew  of  specialists. 

In  bitulithic  pavements,  gravel  or  finely  broken  stone 
soaked  with  asphalt  are  substituted  for  the  complex  mixture 
of  sheet  asphalt  and  similarly  rolled  to  a  smooth,  uniform 
surface  by  steam  rollers.  While  not  as  expensive  as  sheet 
asphalt,  it  has  not  proved  as  durable,  and  it  requires  con- 
stant patching  to  remove  the  holes  and  ruts. 

GRANITOID. — Granitoid  or  concrete  is  occasionally  used      Granitoid. 
for  alley  pavements  where  the  traffic  is  very  light.     While  it 
makes  a  very  clean,  sanitary  pavement,  it  gives  a  very  poor 
foothold  and  rapidly  wears  into  holes  and  ruts.    It  is  scarcely 
to  be  considered  seriously  today,  but  if  the  motor  driven  ve- 


70  VITRIFIED    PAVING    BRICK. 


hide  should  drive  the  horse  out  of  business  in  the  cities,  it 
would  then  rapidly  loom  up  as  a  very  important  paving  ma- 
terial, when  only  a  rubber  tire  would  be  the  principal  de- 
stroying agent. 

COBBLE  STONES. — The  cobble  stone  or  rounded  boulder 
Stone  pavement  is  nearly  a  thing  of  the  past,  except  on  very  steep 
Pavements.  grades  and  in  a  few  ultra  conservative  cities  like  Baltimore. 
They  give  an  excellent  foothold,  are  usually  cheap  and  easily 
repaired,  but  otherwise  they  possess  a  maximum  of  faults, 
not  the  least  of  which  is  their  extreme  noise.  A  lone,  empty 
cart  jolting  over  a  cobble  pavement  makes  such  a  noise  that 
should  cause  their  abolition  in  any  town  that  does  not  have 
to  contend  with  grades  of  over  8  to  10  per  cent.  The  eastern 
cities  formerly  had  a  very  large  mileage  of  these  noisy  pave- 
ments that  are  so  difficult  to  clean,  but  they  have  been  more  or 
less  completely  replaced  by  asphalt,  stone  blocks  or  brick  in 
the  more  progressive  places. 

STONE  BLOCKS. — Stone  blocks  are  very  largely  used  in 
the  down  streets  of  our  large  cities,  as  they  are  capable  of 
successfully  withstanding  the  heaviest  traffic  and  are  the  most 
durable  pavement  known  if  a  hard  rock  is  employed.  Usually 
granite  or  trap  are  employed,  which  can  be  readily  trimmed 
into  regular,  quite  uniform  blocks  that  have  a  toughness  that 
assures  a  very  long  life  under  the  heaviest  traffic.  Sometimes 
local  stone  is  employed  that  is  much  less  durable,  as  sand- 
stones and  limestones,  which,  while  they  vary  greatly  in  their 
wearing  ability,  never  approach  the  durability  of  the  compact 
feldspathic  rocks  like  granite  and  trap. 

While  the  cost  of  a  Belgian  or  stone  block  pavement  varies 
greatly  according  to  the  stone  employed  and  the  distance  it 
has  to  be  shipped,  they  are  usually  the  most  expensive  pave- 
ment to  put  down,  although  their  long  life  and  insignificant 


VITRIFIED    PAVING    BRICK.  71 


maintenance  expenses  make  them  very  economical  to  main- 
tain. 

PRINCIPAL  FACTORS   OF  A  PAVEMENT. 

The  principal  factors  to  be  considered  in  the  selection  of 
a  pavement  are  as  follows: 

1.  First  cost. 

2.  Maintenance. 

3.  Ease  of  traction. 

4.  Foothold  for  the  horses. 

5.  Cleanliness  and  ease  of  cleaning. 

6.  Noise. 

7.  Ease  of  repairing. 

8.  Sanitary  value. 

While  the  relative  value  of  these  different  factors  will 
largely  follow  the  order  as  given,  local  conditions  will  more 
or  less  modify  all  of  them  and  various  authorities  will  materi- 
ally differ  in  the  relative  values  to  be  given  to  each  factor. 

Comparing  the  merits  of  vitrified  brick  with  other  paving 
material  in  meeting  these  conditions,  we  have  the  following 
broad  considerations: 

FIRST  COST.— The  first  cost  is  by  far  the  most  important  First  Cost 
factor  in  the  majority  of  towns  and  cities  of  moderate  size, 
where  the  assessed  value  of  the  property  often  comes  too  un- 
comfortably close  to  the  value  of  the  street  improvements. 
Even  in  our  large  cities,  where  the  much  higher  value  of 
property  eliminates  this  trouble,  many  short  sighted  tax  pay- 
ers are  more  eager  for  the  cheapest  than  the  best  pavement. 

Comparing  vitrified  brick  with  the  other  pavements,  we 
find  that  it  is  much  cheaper  than  stone  blocks,  wood  or  as- 
phalt, but  it  is  usually  considerably  higher  than  macadam. 
These  are  broad  generalizations  and  when  specific  figures  are 
used,  it  must  be  remembered  how  greatly  they  fluctuate  in 


72 


VITRIFIED    PAVING    BRICK. 


Comparison  of 
Costs. 


Maintenance. 


the  same  place,  according  as  the  times,  competition,  labor  and 
other  conditions  vary,  while  a  very  great  range  occurs  when 
different  places  are  compared. 

Usually  the  cost  per  square  yard  of  first-class  pavements 
will  fall  within  the  following  limits: 

USUAL  PAVEMENT  COSTS  PER  SQUARE  YARD. 

Stone  blocks— $2.20  to  $2.50  (up  to  $3.50). 

Creosoted  wood — $2.10  to  $2.50  (up  to  $3.50). 

Asphalt— $2.00  to  $2.50  ($1.60  to  $3.15). 

Vitrified  brick— $1.20  to  $1.75  ($1.00  to  $2.00). 

Macadam  and  telford — 75c  to  $1.50   (40c  to  $2.00). 

MAINTENANCE.— The  maintaining  of  a  pavement  in  first- 
class  condition,  or  the  annual  cost  for  repairs,  is  so  intimately 
associated  with  the  durability  of  a  pavement  that  they  can  be 
considered  as  one  question.  It  is  a  most  elastic,  unsatisfac- 
tory matter  to  discuss,  as,  while  some  very  elaborate  costs  are 
to  be  found  in  current  literature,  some  of  which  emanate  from 
engineers,  that  entitle  them  to  careful  consideration,  the  stand- 
ards differ  so  greatly  in  different  cities  and  in  the  same  city 
under  different  administrations  as  to  make  comparisons  very 
unsatisfactory  and  often  highly  misleading.  Thus  one  city 
will  regard  its  asphalt  streets  as  being  well  maintained  if  they 
are  patched  twice  a  year  at  a  cost  of  2  cents  to  5  cents  per 
square  yard,  while  another  city  has  the  repair  crew  go  thor- 
oughly over  them  at  least  once  a  month,  or  oftener  if  neces- 
sary, and  spends  15  cents  to  25  cents  per  square  yard  annual- 
ly. One  city  will  have  the  repairing  done  by  the  street  de- 
partment that  in  another  place  is  done  by  contract  under  in- 
spectors for  probably  considerably  less  than  half  the  expense. 

Where  a  pavement  is  laid  with  a  five  or  ten  year  main- 
tenance clause,  the  difference  in  opinion  between  the  contrac- 
tor and  the  city  engineer  as  to  when  repairs  are  necessary  is 
often  highly  amusing,  and  not  unfrequently  no  repairs  are 


VITRIFIED    PAVING    BRICK.  73 


made  whatever,  in  spite  of  carefully  drawn  specifications  and 
heavy  bonds. 

The  standards  of  taste  and  the  wealth  of  different  com- 
munities vary  so  greatly  that  what  would  be  regarded  as  a 
satisfactorily  maintained  street  (especially  macadam)  in  one 
place  would  not  be  tolerated  in  another. 

Repair  costs  should  therefore  be  considered  only  in  the 
broadest  way  and  given  only  tentative  values,  unless  all  de- 
tails and  local  conditions  of  a  specific  case  are  fully  given. 

A  good  granite  block  laid  in  a  first-class  manner  is  almost 
exempt  from  any  repairs  for  ten  to  twenty  years  if  not  dis- 
turbed for  pipe  laying,  etc.;  but  as  almost  every  city  street 
is  dug  up  at  least  once  a  year  for  laying  or  repairing  sewers, 
water,  gas,  steam  or  ammonia  pipes,  electric  wire  conduits, 
car  tracks,  etc.,  and  as  the  surface  is  rarely,  if  ever,  properly 
relaid,  even  granite  pavements  need  occasional  repairing, 
which  is  mainly  an  effort  to  restore  the  original  surface.  The 
outlay  is  usually  only  1-10  to  2  cents  per  square  yard  annually, 
which  makes  Belgian  or  stone  pavements  pre-eminently  the 
most  economical  to  maintain.  If  the  stone  have  been  quar- 
ried from,  at  or  near  the  surface,  "weathering"  or  decaying 
may  have  so  softened  apparently  sound  granite  that  it  will 
wear  out  in  ten  to  twenty  years;  but  if  obtained  from  a  depth 
sufficient  to  preclude  weathering  action,  good  granites,  traps 
and  other  felsitic  rocks  should  last  from  twenty-five  to  fifty 
years  under  heavy  traffic. 

A  cobble  stone  pavement  will  have  approximately  half  the 
life  of  a  stone  block  pavement  and  require  more  attention  in 
resetting  them  to  hold  the  boulders  to  grade. 

Brick  pavements  are  almost  as  free  from  repairs  as  gran- 
ite blocks  for  the  first  seven  to  fifteen  years,  according  to  the 
quality  of  the  brick  and  the  amount  of  traffic.  After  that,  oc- 
casional patching  is  required  to  replace  broken  and  worn  out 


74  VITRIFIED    PAVING    BRICK. 


brick,  which  is  an  insignificant  outlay  if  promptly  done,  but 
if  allowed  to  wear  into  ruts,  becomes  decidedly  appreciable, 
or  from  ^  to  3  cents  per  square  yard  annually.  The  ultimate 
life  of  a  high  grade  brick  pavement  is  difficult  to  state,  as  it 
varies  so  greatly  with  the  quality  of  the  brick,  the  care  with 
which  it  is  laid  and  the  density  of  the  traffic  it  bears;  usually 
it  ranges  from  ten  to  thirty  years. 

Wood  pavements  are  also  very  free  from  repairs  for  the 
first  50  to  65  per  cent  of  their  life;  then  the  soft,  decaying, 
imperfect  blocks  begin  to  show  rapidly  and  each  one  starts 
a  chuckhole  that  soon  causes  the  destruction  of  the  adjoining 
blocks,  even  if  sound.  If  it  is  patched  with  new  blocks,  the 
latter  are  so  much  more -resistant  than  the  older,  softer  blocks 
that  each  patch  soon  doubles  the  number  of  chuckholes,  as 
one  forms  on  each  side  of  the  patch.  Patching  soon  becomes 
so  discouraging  that  it  is  usually  abandoned  and  the  street  is 
left  to  its  rough,  rutty,  dirty,  absorbent,  rapidly  retrograding 
condition  until  it  becomes  so  bad  that  the  wooden  blocks  are 
removed  and  usually  replaced  by  either  brick  or  asphalt.  For 
the  last  year  or  two  in  the  life  of  a  wooden  pavement  so  dis- 
gusts the  abutting  property  owners  that  they  will  rarely  tol- 
erate another  wooden  pavement. 

Asphalt  and  bitulithic  macadam  are  by  far  the  most  ex- 
pensive to  maintain.  For  the  2  to  3-inch  surface  of  sheet  as- 
phalt or  bitulithic  macadam  constantly  wears  into  holes  that 
rapidly  widen  if  not  promptly  repaired.  To  maintain  an  as- 
phalt pavement  free  from  holes,  the  repair  gang  should  go 
over  it  at  least  once  a  month,  but  as  this  is  usually  done  by 
contract,  most  pavements  are  allowed  to  go  at  least  six 
months  or  longer,  by  which  time  the  area  to  be  patched  is 
quite  an  important  percentage  of  the  pavement.  The  cost  of 
patching  per  square  yard  will  vary  greatly  according  to  the 
skill,  care  and  efficiency  of  the  repair  gang.  Published  state- 


VITRIFIED    PAVING   BRICK.  75 

ments  as  to  the  cost  differ  so  greatly  as  to  make  it  impossible 
to  make  comparisons  unless  intimately  acquainted  with  the 
local  conditions.  Statements  made  by  reliable  engineers  range 
from  1  to  15  cents  per  square  yard  of  pavement  per  annum, 
but  probably  5  to  12  cents  is  more  nearly  the  average. 

The  bitulithic  needs  more  frequent  repairs,  but  as  they  are 
more  cheaply  made  than  with  the  sheet  asphalt,  the  cost  of 
maintenance  will  fall  within  the  above  figures. 

BASE   OF   TRACTION. 

The  power  required  to  haul  a  given  load  over  the  different 

pavements  varies  greatly,  and  while  this  is  a  more  important  Case  of  Traction. 
factor  with  business  vehicles,  it  is  also  a  factor  with  pleasure 
outfits.  With  this  should  also  be  considered  the  relative  wear 
and  tear  of  the  harness  and  rig,  which  will  be  found  to  ap- 
proximately vary  as  the  tractive  resistance,  especially  with 
automobiles.  Asphalt  leads  in  this  respect,  but  is  closely  fol- 
lowed by  brick  and  wood,  when  the  latter  is  in  good  condi- 
tion. Stone  blocks  are  much  inferior,  while  cobble  cobble 
stone  pavements  are  atrocious. 

Macadam  varies  greatly,  according  to  the  condition  in 
which  it  is  maintained.  If  kept  damp  and  free  from  ruts,  it 
is  superior  to  granite;  but  if  it  ranges  from  a  very  dusty  to 
muddy  condition,  it  is  decidedly  inferior  to  granite.  A  rela- 
tive comparison  of  the  traction  of  the  same  load  over  differ- 
ent pavements  as  well  as  dirt  and  loose  is  given  by  Ru- 
dolph Hering,  the  eminent  civil  engineer,  as  follows: 

COMPARATIVE  HAULAGE  OF  A  GIVEN  LOAD  ON: 

Iron  rails 1  horse 

Sheet  asphalt  (good  condition) 1.7  horse 

Brick 2.25  to  2.75  horse 

Granite  blocks 3.3  to  5.  horse 

Wood ..5.  to  6.  horse 


76  VITRIFIED    PAVING    BRICK. 

Good   macadam 8.   horse 

Cobble  stones 7.  to  13.  horse 

Earth 20.    horse 

Sand 40.    horse 

FOOTING. — A   sure   footing   for   the   horses    and   freedom 
from  slipping  is  an  important  factor  of  a  pavement,  in  which 
asphalt   and   rectangular  wooden   blocks   are   very   defective. 
•  The  joints  of  brick  and  granite  blocks  hold  the  calks  of  a 

horse's  shoe  and  are  therefore  very  satisfactory.  Macadam 
and  cobble  stones  are  more  efficient  and  on  very  heavy  grades, 
or  over  10  per  cent,  are  the  only  pavements  that  should  be 
used.  Brick  and  granite  can  be  used  up  to  10  per  cent  grades, 
but  asphalt  or  wood  should  not  be  used  if  the  grade  exceeds 
3  per  cent.  For  automobile  service,  this  factor  disappears. 

CLEANLINESS  AND  EASE  OF  CLEANING. 
The  hard  pavements,  or  stone,  brick  and  asphalt,  do  not 
Cleanliness,  produce  through  wear  any  dirt  that  is  of  consequence  and 
wood  is  also  practically  free  from  it  until,  through  decay,  it 
gets  into  a  soggy,  spongy  condition.  Macadam,  on  the  con- 
trary, unless  maintained  in  an  ideal  condition  of  dampness 
that  is  rarely  seen  and  protected  from  heavy  traffic,  produces 
so  much  dust  in  dry  weather  and  is  so  muddy  in  wet  weather 
or  from  imperfect  sprinkling  that  it  should  not  be  tolerated 
in  large  cities  where  the  value  of  the  land  justifies  the  best 
pavements.  The  cleaning  of  macadam  pavements  is  also 
very  costly,  as  it  has  to  be  done  by  hand  labor,  as  sweeping 
machines  or  the  hydraulic  systems  destroy  it.  The  hard  pave- 
ments can  all  be  cleaned  by  sweeping  machines,  but  the  re- 
sults are  not  satisfactory  on  stone  pavements  on  account  of 
their  roughness  and  the  large  joints,  while  the  wear  is  heavy 
on  the  brooms  of  the  machine.  The  flushing  or  the  hydraulic 
systems  (which  are  the  most  efficient  and  cheapest)  can  be 


VITRIFIED    PAVING    BRICK. 


77 


used  on  all  hard  pavements,  but  the  water  shortens  the  life 
of  asphalt  by  slowly  disintegrating  it  through  a  solution  of 
the  binding  oils. 

NOISE. — This  is  a  very  important  factor  in  large  cities, 
but  its  importance  will  vary  with  local  conditions.  It  is  not 
so  serious  in  a  manufacturing  community  as  it  is  in  the  resi- 
dential quarters  and  especially  about  schools,  churches,  court 
houses,  etc.  All  the  durable  pavements  are  open  to  more  or 
less  criticism,  although  in  most  cases  this  factor  is  subordi- 
nated to  the  much  more  vital  questions  of  cleanliness  and 
durability.  Wood  makes  a  pavement  that  is  practically  noise- 
less and  for  this  reason  it  has  quite  a  popularity  in  large 
cities  in  spite  of  its  other  numerous  defects.  The  business 
portion  of  London  submits  to  its  streets  being  torn  up  every 
four  to  seven  years  to  relay  the  worn  out  wood  pavements  in 
order  to  get  rid  of  the  roar  that  stone  pavements  would  cause. 
Macadam  and  telford  are  also  noiseless,  but  the  excessive 
annoyance  from  dust  and  mud  and  the  constant  repairs  ren- 
der them  too  objectionable  in  large  cities.  Brick  pavements 
cause  only  a  moderate  amount  of  noise  that  is  rarely  objec- 
tionable, and  it  is  free  from  the  sharp  click  of  the  horses' 
hoofs  that  is  characteristic  of  asphalt.  Stone  blocks  are  very 
noisy,  both  from  the  click  of  the  horses'  hoofs  and  the  rumble 
of  the  wagon  tires,  but  the  worst  offender  is  the  cobble  stone 
pavement,  over  which  a  lone,  empty  cart  causes  a  thunder 
that  would  warrant  a  board  of  health  in  condemning  it  as  a 
public  nuisance. 

EASE  OF  REPAIRS.— The  repairs  to  a  pavement  come 
under  two  categories — that  due  to  natural  wear  and  tear  and 
that  caused  by  the  frequent  tearing  up  of  the  street  for  laying 
pipes,  conduits,  etc.  The  life  of  all  pavements  would  be  very 
considerably  prolonged  if  they  were  not  disturbed  after  once 
being  properly  laid.  For  when  a  pavement  is  torn  up  for  pipe 


Noise. 


Ease  of  Repairs. 


78  VITRIFIED    PAVING    BRICK. 


laying,  etc.,  the  foundation  is  rarely  replaced  in  proper  con- 
dition, so  that  through  subsequent  settling  the  surface  of  the 
pavement  is  more  or  less  severely  thrown  out  of  line.  This 
causes  excessive  wear  and  injury  to  the  pavement,  especially 
as  the  defect  is  rarely  remedied  until  it  has  become  very 
bad.  The  time  is  not  far  distant  when  our  large  cities  will  no 
longer  tolerate  this  frequent  abuse  of  the  pavements  and 
temporary  disuse  of  the  street,  as  tunnels  will  be  insisted  on 
for  carrying  the  pipes,  wires,  conduits,  etc.,  in  which  altera- 
tions, repairs,  etc.,  can  be  made  without  disturbing  the  pave- 
ment. 

While  stone  pavements  are  the  easiest  to  repair,  they  are 
closely  followed  by  brick,  and  the  most  troublesome  is  as- 
phalt. 

SANITARY  VALUE. — A  jointless  pavement  presents  the 
Sanitary  Value,  smoothest  surface  to  prevent  the  lodgement  of  filth  and  to 
enable  rains  or  flushing  to  thoroughly  cleanse  it.  Asphalt  is, 
therefore,  the  most  sanitary  pavement,  while  stone  blocks  and 
cobble  stones  are  the  worst.  A  wood  pavement,  if  made  from 
closely  fitting  rectangular  blocks,  is  excellent  at  first,  but  it 
soon  wears  into  ruts  and  holes,  in  which  the  filth  finds  lodge- 
ment and  later,  as  the  wooden  blocks  decay,  they  give  off  un- 
pleasant odors.  Brick  makes  a  good,  sanitary  pavement,  es- 
pecially if  the  small  joints  are  grouted  with  cement,  which 
latter  is  now  the  standard  practice.  The  very  remarkable 
record  made  by  the  U.  S.  Engineer  Corps  at  Panama,  which, 
from  being  the  most  unhealthy  city  in  the  world,  with  a 
frightful  mortality  from  yellow  fever,  has  been  changed  to  a 
healthy  city,  has  been  largely  attributed  to  vitrified  brick. 
For  not  only  have  the  streets  been  paved  with  brick,  but  also 
the  sewers,  so  that  between  flushing  by  rains  and  with  hose, 
a  state  of  cleanliness  has  resulted  that  has  tremenduously 
lowered  the  death  rate  and  nearly  made  the  hospitals  useless. 


VITRIFIED    PAVING    BRICK. 


79 


SIZE  OF  BRICK. — When  the  manufacture  of  vitrified  brick 
for  paving  first  became  an  established  industry,  the  brick- 
makers  patterned  their  work  after  granite  blocks.  They  soon 
found  that,  it  was  very  difficult  to  insure  thoroughness  and  uni- 
formity in  burning  such  large  sizes,  especially  as  the  blunder 
was  made,  and  to  some  extent  is  still  perpetrated,  of  giving 
them  an  appearance  of  thorough  vitrification  by  salt-glazing, 
and  many  brick  pavements  were  justly  condemned  for  the 
failure  due  to  the  soft  brick  that  resulted.  Against  the  pro- 
test of  engineers,  many  manufacturers  changed  to  the  size  of 
building  brick,  and  the  marked  improvement  in  quality  and 
uniformity  speaks  for  their  good  judgment,  and  has  converted 
most  engineers  who  have  had  much  experience  with  paving 
brick.  Today  there  are  two  sizes  in  the  market,  or  standard 
and  block.  The  standard  size  is  about  8^x4x2%  inches,  or 
the  same  as  building  brick,  while  the  block  size  is  about  9x4x 
3  inches.  Each  size  has  its  advocates,  but  the  best  records 
have  been  made  in  the  pavement  by  the  standard  size. 

Formerly  brick  were  made  with  square  or  but  slightly 
rounded  edges  and  corners,  but  the  sharp  corner  soon  chips 
off  under  wear,  and  until  so  chipped  it  makes  a  poor  footing 
for  the  horses,  on  account  of  the  tightness  of  the  joints.  Brick 
are  now  made  with  rounded  corners,  using  a  radius  of  one- 
quarter  to  three-eighths  inch,  which  makes  a  more  durable 
brick  and  furnishes  a  much  better  footing. 

Some  of  the  blocks  on  the  market  are  patented,  the  patent 
being  based  on  various  shaped  grooves  and  lugs  pressed  into 
their  flat  sides  to  assist  in  holding  the  tar  or  other  filler,  and 
of  these  the  Hallwood  patent  is  one  of  the  best  known,  which 
is  made  by  several  concerns  on  a  royalty.  The  grooves  and 
lugs  are  not  found  necessary  if  the  brick  are  laid  on  a  good 
foundation,  and  their  value  is  greater  as  a  trade-mark  than 
for  their  intrinsic  merit  for  paving  purposes. 


Blocks. 


Common  Size. 


Rounded 
Corners. 


Grooves  and 
Lugs. 


80 


VITRIFIED    PAVING    BRICK. 


Sand  Cushion. 


Concrete  the  FOUNDATIONS. — The   success  of  any  pavement  depends 

Standard,  primarily  on  a  good  foundation,  and  brick  must  have  a  good 
foundation  if  a  smooth,  durable  pavement  is  desired.  In  the 
early  experience  of  our  brick  pavements,  the  enthusiasm  of 
the  brick  advocates  went  so  far  as  to  claim  that  brick  would 
be  satisfactory  on  any  kind  of  a  foundation,  and  very  poor  sup- 
ports, such  as  sand,  plank,  etc.,  were  put  under  some  of  the 
early  pavements,  with  the  disappointing  results  that  were 
bound  to  follow.  Engineers  have  been  quick  to  see  this  and 
insist  on  a  good  foundation,  so  that  a  concrete  base  is  now 
the  standard  foundation.  The  concrete  is  made  eight  inches 
thick  for  heavy  traffic,  six  inches  for  moderate,  and  four  inches 
for  very  light  traffic.  Where  the  travel  will  not  bear  the  ex- 
pense of  concrete,  broken  stone,  gravel,  or  cinders  have  been 
substituted,  thereby  saving  the  expense  of  the  cement  and 
mixing.  A  still  cheaper  foundation  that  has  been  largely  used 
in  the  small  cities  and  towns  is  to  use  a  four  to  six-inch  bed 
of  sand,  on  which  is  laid  a  course  of  No.  2  pavers  placed  flat- 
wise. 

Whether  the  foundation  be  concrete,  gravel  or  brick,  a 
cushion  of  sand  is  always  used  between  it  and  the  top  course 
of  brick,  to  take  up  the  unevenness  of  the  surface  of  the  foun- 
dation and  any  irregularities  in  the  brick.  This  sand  cushion 
is  usually  two  inches  thick,  but  the  writer  thinks  it  should  be 
reduced  to  one  inch,  as  this  is  sufficient  if  the  foundation  is 
leveled  up  with  care,  and  the  thinner  the  cushion  the  less  the 
risk  of  the  brick  settling  or  getting  displaced  in  service.  The 
Fillers.  toP  course  of  brick  are  laid  on  edge  at  right  angles  to  the 
street,  and  at  45  degrees  at  intersections,  and  the  joints  be- 
tween the  brick  are  filled  with  cement  grouting,  tar,  pitch  or 
sand.  A  cement  filling,  if  of  Portland  cement,  binds  the  brick 
into  a  monolith,  and  gives  the  best  results,  as  it  is  not  affected 
by  hot  weather.  Tar  or  pitch  is  also  a  good  binder  and  filler, 


VITRIFIED    PAVING    BRICK.  81 


but  it  softens  in  hot  weather,  though  this  enables  broken 
joints  to  reunite,  which  is  not  the  case  with  cement.  In  either 
case  the  grouting  or  tar  should  be  thin  when  applied,  so  that 
it  can  penetrate  into  the  joints,  which  are  usually  only  one- 
sixteenth  to  one-eight  inch  wide.  Sand  filling  is  much  cheap- 
er, and  permits  the  easy  removal  of  the  brick  for  pipe  laying, 
etc.,  and  when  once  well  worked  in  makes  a  solid  pavement; 
but  too  frequently  it  is  improperly  applied  by  not  having  it 
perfectly  dry  and  clean,  when  very  little  of  it  works  into  the 
cracks,  no  matter  how  persistently  it  is  swept*  over  the  sur- 
face. Before  the  filling  is  applied,  the  bricks  are  carefully 
rolled  to  a  true,  uniform  surface  with  a  heavy  roller,  after 
which  any  broken  or  chipped  brick  are  replaced,  and  after 
the  pavement  is  finally  thrown  open  to  traffic  a  half-inch  layer 
of  sand  is  left  on  top  for  a  month  or  so,  to  insure  thorough 
filling  of  the  joints. 

DRUMMING. — When  brick  are  laid  in  cool  weather  and  a  Drummjn 
cement  filler  is  employed,  there  is  frequently  a  hollow,  drum- 
ming sound  in  the  hot  weather  when  a  horse  trots  over  it. 
This  is  due  to  the  heat  expanding  the  brick  so  that  the  pave- 
ment slightly  arches  or  bridges  between  the  curbstones  and 
raises  off  from  the  sand  cushion  to  a  moderate  extent.  When 
cool  weather  returns  the  brick  contract,  the  arching  ceases 
and  the  noise  disappears.  To  avoid  this  trouble,  a  wide  joint 
should  be  left  at  or  near  and  parallel  with  the  gutter  line  that 
is  filled  with  tar  or  asphalt.  As  the  latter  softens  and  yields 
in  hot  weather,  it  prevents  the  pavement  from  arching  or 
rising  off  of  the  sand  cushion. 


*Unless  the  sand  is  perfectly  dry,  it  is  better  to  flush  it  in 
with  water,  rather  than  attempt  to  work  it  in  with  a  broom 
by  sweeping. 


82  VITRIFIED    PAVING    BRICK. 


Life  of  Brick  LIFE    OF    BRICK    PAVEMENTS.— As    about    forty    years 

Pavements.  have    elapsed    since   the    first   brick    pavement    was    laid    in 

Charleston,  W.  Va.,  and  it  is  some  twenty  years  since  they 
have  been  extensively  used,  there  is  now  considerable  data  on 
which  to  base  an  opinion  as  to  the  usual  life  of  vitrified  brick. 
There  were  naturally  a  good  many  poor  brick  turned  out  in 
the  early  pioneer  days  of  the  industry  before  the  details  for 
the  successful  manufacture  of  vitrified  brick  were  understood 
and  before  it  was  realized  that  comparatively  few  clays  or 
shales  are  suitable  for  a  high  grade  brick.  Quite  a  number  of 
the  early  brick  pavements  have,  therefore,  been  renewed  and 
also  some  more  recent  ones  that  were  laid  when  there  was 
such  a  boom  that  some  contractors  would  take  anything  that 
came  from  a  factory  with  a  paving  brick  tag.  Since  a  stand- 
ard method  of  testing  has  been  adopted  and  with  the  elimina- 
tion of  factories  that  did  not  have  suitable  clays  or  equipment, 
a  much  better  grade  of  brick  has  been  put  on  the  market. 
Comparing  the  grade  of  brick  on  the  market  today  by  the 
rattler  test  with  those  that  lasted  ten  to  twenty-five  years  in 
actual  use,  it  is  safe  to  say  that  the  vitrified  brick  that  can 
make  a  fair  rattler  test  should  last  from  twelve  to  twenty- 
five  years  under  moderate  business  traffic,  and  for  fifteen  to 
thirty  years  when  high  grade.  This  is  based  on  the  brick  hav- 
ing a  good  foundation  and  being  properly  laid — a  matter  that 
is  now  well  understood  and  usually  insisted  on  by  municipal 
engineers.  Extra  good  brick  will  have  a  naturally  longer  life 
than  the  above,  while  the  heavy  traffic  of  the  downtown 
streets  in  a  large  city  will  more  or  less  shorten  the  life. 

The  block  on  LaSalle  street,  Chicago,  opposite  the  County 
Court  House,  was  laid  with  Purington  brick  (standard  size) 
about  fifteen  years  ago.  Although  the  pavement  has  been 
torn  up  with  exceptional  frequency  and  it  has  been  subjected 


VITRIFIED    PAVING    BRICK. 


to  about  the  heaviest  traffic  of  Chicago,  it  is  still  in  fair  con- 
dition and  should  last  several  years  longer. 

The  first  brick  pavement  laid  in  the  United  States  at 
Charleston,  W.  Va.,  lasted  thirty-five  years,  and  while  it  is 
not  a  large  city  (12,000),  the  brick  were  made  from  a  surface 
clay  and  were  really  a  very  hard  burned  building  brick. 

DETAILED   COST   OF   BRICK   PAVEMENT. 

While  the  cost  of  brick  pavements  will  vary  more  or  less      Detailed  Cost  of 
in  different  places   and   also  in  the   same  place  at  different      Brick  Pavement. 
times,  according  to  the  changes  in  local  markets,  conditions, 
etc.,  the  following  generalized  estimate  from  Baker's  "Roads 
and  Pavements,"  page  521,  will  give  an  idea  as  to  how  the 
cost  is  distributed.     This  is  based  on  municipal  work  as  per- 
formed by  contractors: 

Cost  per  sq.  yd. 

Sub-grade    rolling    $0.002 

Concrete,  6  inches,  materials 0.40 

Labor    of    laying 0.07 

Sand  cushion,  2  inches  sand  at  90c  per  cu.  yd 0.05 

Labor   of   spreading 0.005 

Brick  blocks,  4-in.  deep;  cost  f.  o.  b.  cars  destination 0.60 

Hauling  to   street 0.04 

Setting    0.03 

Rolling    0.003 

Turning  and  removing 0.01 

Portland  cement  grout,  1  to  1  mixture 0.10 

Expansion  joint,  tar,  1  gal.  to  5  square  yards 0.015 


Total     $1.33 

This  cost  of  $1.33  per  square  yard  does  not  include  admin- 
istration, wear  and  tear  of  tools,  nor  contractor's  profit,  which 
will  usually  bring  the  contractor's  price  up  to  $1.50  to  $1.60 
per  square  yard. 


84  VITRIFIED    PAVING    BRICK. 

PAVING  STATISTICS. 

Paving  To  show  the  relative  popularity  of  the  different  pavements 

Statistics,  in  the  year  1900  in  129  cities  of  the  United  States  that  had  a 
population  of  30,000  or  more,  the  following  figures,  collected 
by  the  U.  S.  Department  of  Labor  and  published  in  their  bul- 
letin No.  24  (September,  1900),  is  quite  interesting: 

Asphalt    36,585,322  sq.  yds.  at  $2.75=$100,609,635 

Brick     21,648,768  sq.  yds.  at    1.75=     37,885,344 

Cobble    stone 21,600,245  sq.  yds.  at      .80=     17,280,196 

Granite    block 30,816,521  sq.  yds.  at    3.50=107,857,823 

Gravel    38,645,022  sq.  yds.  at      .20=      7,729,004 

Macadam    82,680,545  sq.  yds.  at      .75=     62,010,409 

Wood    blocks 27,727,572  sq.  yds.  at    1.25=     34,659,465 

Other  kinds  [9,553,000  sq.  yds.  at    2.50=     23,882,500 

8,888,200  sq.  yds.  at    1.00=       8,888,200 


Total     278,145,195  sq.  yds.  costing     $400,812,576 

The  values  in  the  above  table  have  been  estimated  by  Prof. 
Baker,*  and  while  only  approximate,  it  illustrates  the  magni- 
tude of  the  investment  in  the  larger  towns  and  cities. 

Of  the  large  cities  that  use  brick  extensively,  Philadelphia, 
St.  Louis  and  Chicago  have  been  in  the  lead,  and  the  follow- 
ing table  not  only  brings  out  the  increasing  growth  in  the 
use  of  brick,  but  also  the  decline  in  the  use  of  wood  and  cob- 
ble stone  pavements  when  the  three  periods  of  1890,  1900  and 
1906  are  compared: 


*Page  293,  Baker's  Roads  and  Pavements. 


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86  VITRIFIED    PAVING    BRICK. 

SPECIFICATIONS    FOR    BRICK   PAVING. 

Specifications.  To  illustrate  the  type  of  contracts  that  are  drawn  up  for 

brick  paving,  the  following  example  is  given  from  the  St. 
Louis  street  department,  which  is  the  form  on  which  contract- 
ors make  up  their  bids  in  bidding  for  street  work,  which  is 
let  after  advertising,  to  the  lowest  bidder.  It  will  be  noted 
that  it  calls  for  a  cross-breaking  strength  of  over  2,000  pounds 
per  square  inch  and  an  absorption  not  greater  than  2.0  per 
cent  if  the  rattler  loss  is  not  over  25  per  cent.  When  the 
rattler  loss  is  less  than  20  per  cent,  then  an  absorption  as 
great  as  4.0  per  cent  is  allowed. 

The  St.  Louis  street  department  has  always  been  partial 
to  the  cross-breaking  test  for  bringing  out  the  uniformity  and 
care  exercised  in  making  the  brick,  which  quickly  shows  up 
in  this  test.  The  2  per  cent  absorption  prejudice  is  a  survival 
of  the  former  idea  that  most  engineers  had  that  no  paving 
brick  could  be  relied  on  to  withstand  frost  action  if  it  ab- 
sorbed over  2  per  cent,  although  extra  tough  brick  that  suffer 
a  loss  of  less  than  20  per  cent  are  conceded  to  be  safe  if  the 
absorption  is  as  high  as  4.0  per  cent: 

CLASS  "BC"  CONTRACT  AND  SPECIFICATIONS  FOR  VIT- 
RIFIED BRICK   STREET   CONSTRUCTION, 
GRANITE  CURB. 

AGREEMENT,  Made  and  Entered  into  this 

day  of A.  D.  190 ,  by  and  between 

part of    the 

first  part,  and  the  "City  of  St.  Louis,"  party  of  the  second 
part,  witnesseth: 

Whereas,  The  Board  of  Public  Improvements  of  the  said 

City  of  St.  Louis  under  the  provisions  of  Ordinance  No 

approved and  by  virtue   of  the   authority 

vested  in  the  said  Board  by  the  charter  and  the  general  or- 


VITRIFIED    PAVING    BRICK. 


87 


dinances  of  the  City  did  let  unto  the  said  part of  the  first 

part  the  work  of  improving 

by  grading  and  preparing  the  roadbed  for  the  superstructure, 
furnishing  granite  curbing  and  setting  the  same  in  Portland 
cement  concrete;  laying  a  roadway  pavement  to  consist  of  a 
base  of  Portland  cement  concrete,  and  a  wearing  surface  com- 
posed of  the  best  quality  of  vitrified  paving  brick;  making  all 
proper  connections  and  intersections  with  other  streets  and 
alleys,  and  guaranteeing  to  keep  in  repair  all  of  the  aforesaid 
work  and  materials  for  a  term  of  five  years,  commencing  on 
the  date  of  acceptance  of  the  work  of  improvement,  as  speci- 
fied by  the  above  mentioned  ordinance. 

NOW,  THEREFORE,  In  consideration  of  the  payments  and 
covenants  hereinafter  mentioned,  to  be  made  and  performed 
by  said  second  party,  the  said  first  part  hereby  covenant 
and  agree  to  do  the  work  above  mentioned  in  a  substantial 
and  workmanlike  manner,  in  conformity  with  the  plans  of 
such  work  on  file  in  the  offices  of  the  Board  of  Public  Im- 
provements and  the  Street  Commissioner  of  the  City  of  St. 
Louis  and  in  accordance  with  the  following: 

SPECIFICATIONS. 

GRADING    AND    PREPARING    THE    ROADBED    FOR    THE 
SUPERSTRUCTURE. 

The  grading  and  preparing  the  roadbed  for  the  superstruc- 
ture will  include  all  excavating  or  filling  necessary  to  bring 
the  sub-grade  to  a  surface  which  will  conform  to  and  be  paral- 
lel with  the  grade  of  the  finished  pavement  and  the  sloping 
of  -intersecting  streets  or  alleys.  Any  trees  or  stumps  on  or 
near  the  work  will  be  grubbed  without  extra  charge.  All  sur- 
plus earth  or  macadam  shall  be  hauled  to  such  city  property 
within  a  distance  of  2,000  feet  as  the  Street  Commissioner 
may  designate  and  spread  according  to  his  directions;  but  if 


Grading  and 

Preparing 

Roadbed. 


88  VITRIFIED    PAVING    BRICK. 


no  such  place  is  designated,  the  material  shall  belong  to  the 
contractor  and  removed  from  the  work  by  him.  Where  the 
embankment  is  in  excess  additional  material  for  filling  shall 
be  furnished  by  the  contractor. 

Embankments  must  be  spread  in  layers  not  exceeding  one 
foot  in  depth  and  shall  consist  of  clean,  dry  earth,  stone,  sand, 
gravel  or  other  similar  material.  No  refuse,  vegetable  matter 
or  debris  of  any  kind  will  be  permitted  in  the  fill.  No  allow- 
ance will  be  made  for  settlement  or  shrinkage,  and  payment 
will  be  made  only  on  quantities,  as  shown  by  cross-sections, 
for  excavation  or  embankment,  which  ever  is  in  excess. 

The  roadbed  shall,  wherever  practicable,  be  thoroughly 
rolled  and  compacted  with  a  roller,  weighing  not  less  than 
eight  tons,  or  a  roller  that  will  give  a  compression  of  three 
hundred  pounds  for  each  inch  width  of  roller.  All  places  that 
can  not  be  reached  by  a  roller  shall  be  rammed  with  hand 
rammers,  weighing  not  less  than  ninety  pounds.  If  depres- 
sions appear,  or  if  in  the  opinion  of  the  Street  Commissioner 
any  of  the  material  in  the  sub-grade  is  spongy  or  otherwise 
unfit  to  be  used,  he  may  order  the  same  removed  and  the  ex- 
cavation refilled  with  stone,  sand,  gravel  or  other  satisfactory 
material.  After  this  refilling  the  roadbed  shall  be  re-rolled 
until  it  is  brought  to  a  true,  even  and  compact  surface.  The 
price  bid  per  cubic  yard  for  grading  and  preparing  the  roadbed 
for  the  superstructure,  will  include  all  work  above  mentioned 
necessary  to  bring  the  sub-grade  to  the  proper  shape  and 
elevation,  except  the  removal  of  unsuitable  material  below  the 
sub-grade,  which  will  be  paid  for  both  ways  at  the  price  bid 
for  grading. 


INTERSECTION  WITH  STREETS  AND  ALLEYS. 

^herever    the    work    joins    unimproved    or    macadan 

streets   and   alleys,   and   the   Street   Commissioner   deems   it 


Intersections.  Wherever    the    work    joins    unimproved    or    macadamized 


VITRIFIED    PAVING    BRICK.  89 


necessary,  it  shall  be  protected  by  macadam  spread  behind 
the  marginal  curb  hereinafter  described.  Where  the  work 
joins  a  paved  street  or  alley,  all  old  paving  damaged  during 
the  construction  work  shall  be  carefully  replaced  by  the  con- 
tractor at  his  own  expense  to  the  satisfaction  of  the  Street 
Commissioner;  provided,  however,  that  if  said  street  or  alley 
is  under  a  maintenance  contract,  the  contractor  having  said 
maintenance  in  his  charge  shall  be  permitted  to  make  the  re- 
pairs required  and  be  paid  for  them  in  accordance  with  the 
terms  of  his  contract,  at  the  sole  expense  of  the  party  of  the 
first  part  under  this  contract. 

CEMENT. 

All  cement  to  be  used  on  the  work  herein  specified  shall      Cement. 
be  of  the  best  quality  of  Portland  cement,  delivered  in  suitable 
packages  with  the  name  of  the  manufacturer  plainly  marked 
thereon. 

It  shall  be  subject  to  inspection  and  samples  furnished  for 
the  following  tests  at  any  time: 

1.  Specific   Gravity:      When   thoroughly  dried   at   100   de- 
grees C.  the  specific  gravity  shall  be  not  less  than  3.10. 

2.  Fineness:      It  shall  have  by  weight   a  residue  of  not 
more  than  8  per  cent  on  a  No.  100  sieve  and  not  more  than 
25  per  cent  on  a  No.  200  sieve. 

3.  Time  of  Setting:     It  shall  not  develop  initial  set  in  less 
than  forty-five  minutes  nor  final  set  in  less  than  one  and  one- 
half  hours  nor  more  than  ten  hours. 

4.  Tensile  Strength:     Briquettes  one  square  inch  in  sec- 
tion made  of  neat  cement  must  develop  tensile  strength  as 
follows:  one  day  in  air  and  six  days  in  water  500  pounds,  one 
day  in  air  and  twenty-seven  days  in  water  650  pounds;   when 
mixed  with  three  parts  of  sand  by  weight:  one  day  in  air  and 


90  VITRIFIED    PAVING    BRICK. 


six  days  in  water  250  pounds,  one  day  in  air  and  twenty-seven 
days  in  water  325  pounds. 

The  twenty-eight  day  test  must  show  an  increase  of  at 
least  15  per  cent  over  the  seven  day  test  in  the  mortar  bri- 
quettes. 

Cement  passing  the  requirements  of  the  seven  day  test 
may  be  used  at  once,  or  held  for  the  twenty-eight  day  result, 
at  the  option  of  the  Street  Commissioner. 

5.  Soundness:     Two  pats  of  neat  cement  shall  be  made 
about  three  inches  in  diameter  and  one-half  inch  thick  at  the 
center,  tapering  to  a  thin  edge.    These  pats  will  be  kept  moist 
until  finally  set,  when  one  will  be  placed  in  fresh  water  for 
seven  days  and  the  other  in  water  which  will  be  raised  to  the 
boiling  point  for  six  hours  then  allowed  to  cool.     Neither  of 
the  pats  must  show  distortion  or  cracks. 

6.  Sulphuric  Acid  and  Magnesia:     The  cement  shall  not 
contain  more   than   1.75   per   cent   anhydrous   sulphuric   acid 
(SOS)  and  not  more  than  4  per  cent  magnesia  (MgO). 

SAND    OR    LIMESTONE    SCREENINGS. 

If  sand  is  used  in  the  mortar  for  concrete  it  shall  be  clean, 
coarse,  screened  Mississippi  River  or  Meramec  River  channel 
sand,  and  if  limestone  screenings  are  used,  they  shall  pass 
through  a  sieve  having  sixteen  meshes  to  the  square  inch  and 
shall  be  free  from  all  dirt  and  rubbish. 

BROKEN   STONE   OR   WASHED   GRAVEL. 

The  broken  stone  or  washed  gravel  used  in  the  concrete 
shall  be  any  hard  rock  satisfactory  to  the  Street  Commission- 
er and  of  such  a  size  that  it  will  pass  through  a  two  and  one- 
half  inch  ring  and  be  retained  by  a  one-half  inch  ring.  When 
delivered  on  the  work  it  shall  be  deposited  on  a  hard,  clean 
surface  and  if  such  a  surface  is  not  available,  it  shall  be  de- 
posited and  kept  on  plank  until  used. 


VITRIFIED    PAVING    BRICK. 


91 


CONCRETE. 

Concrete  shall  be  mixed  in  the  following  manner  and  pro- 
portions by  volume: 

One  part  of  cement  and  four  parts  of  sand  shall  be  thor- 
oughly mixed  dry,  after  which  a  sufficient  quantity  of  water 
shall  be  added  to  produce  a  mortar  of  the  proper  consistency. 
To  this  mortar  will  be  added  seven  parts  of  wet  broken  stone 
or  washed  gravel  and  the  whole  thoroughly  mixed  in  any 
manner  satisfactory  to  the  Street  Commissioner. 

The  concrete  thus  prepared  will  be  immediately  spread  on 
the  sub-grade  and  rammed  and  compacted  so  as  to  produce  a 
uniformly  dense  mass  six  inches  thick. 

No  walking  or  driving  over  concrete  in  place  must  be  per- 
mitted while  it  is  setting,  and  it  shall  be  allowed  to  set  for  at 
least  five  days  and  such  additional  length  of  time  as  may  be 
directed  by  the  Street  Commissioner,  before  the  pavement  is 
put  upon  it. 

Before  placing  fresh  concrete  against  that  which  is  already 
set,  the  old  concrete  must  be  thoroughly  cleaned  and  wet  so 
that  the  new  work  may  readily  form  a  bond  with  the  old. 

CURBING. 

All  curbing  shall  be  of  the  best  quality  of  granite,  equal  in 
material  and  finish  to  the  sample  in  the  Street  Commissioner's 
office  and  the  stones  shall  be  not  less  than  sixteen  inches  deep, 
six  inches  thick  and  four  feet  long.  The  bottom  bed  shall  be 
roughly  squared.  The  top  and  face  shall  have  a  rough  pean 
hammer  finish,  the  face  dressed  to  the  full  depth  of  the  stone 
and  shall  in  no  place  vary  more  than  three-eighths  of  an  inch 
from  a  true  plane.  The  back  of  the  stone  shall  be  dressed 
parallel  to  the  face  a  depth  of  four  inches  below  the  top. 
Special  care  must  be  taken  to  cut  the  joints  square  with  the 


Concrete. 


Curbing. 


92  VITRIFIED    PAVING    BRICK. 


face  and  top,  and  the  joints  shall  be  close  for  the  full  thick- 
ness and  depth  of  the  stone. 

It  shall  be  brought  and  kept  to  proper  line  and  grade  by 
using  not  more  than  two  stone  props,  not  to  exceed  ten  inches 
in  width  for  each  piece  of  curb.  It  shall  rest  on  concrete  of 
the  quality  hereinbefore  specified,  six  inches  deep  and  twelve 
inches  wide,  and  shall  be  backed  with  concrete  six  inches 
wide  and  ten  inches  deep  or  to  a  line  six  inches  below  the 
top  of  the  curb.  After  the  curb  is  set,  the  concrete  shall  be 
carefully  forced  and  rammed  below  and  behind  the  curb  until 
it  fully  rests  upon  and  is  backed  with  concrete,  as  above  de- 
scribed. 

Care  must  be  taken  not  to  disturb  or  break  the  sidewalk 
pavement  more  than  necessary,  and  in  all  cases,  unless  other- 
wise directed,  it  shall,  when  broken,  be  fully  restored  at  the 
expense  of  the  contractor. 

Wherever  in  connecting  with  sewer  inlets  or  old  curbing, 
the  joints  are  found  to  be  too  wide,  they  shall  be  filled  with 
mortar  consisting  of  one  part  of  Portland  cement  and  two 
parts  of  sand,  at  the  contractor's  expense. 

No  curbing  will  be  set  until  the  rough  grading  has  been 
done  and  the  concreting  must  be  done  in  advance  of  the 
street  concreting. 

The  price  bid  per  lineal  foot  for  granite  curb,  shall  include 
the  curb  set  complete. 

MARGINAL  CURB. 

At  all  places  where  the  pavement  ends  and  where  it  is  not 
protected  by  the  granite  curbing,  a  marginal  curb  shall  be 
placed  if  the  Street  Commissioner  so  directs.  This  curb  shall 
be  made  of  oak  plank  two  inches  thick  and  twelve  inches 
wide  and  shall  be  set  on  six  inches  of  concrete,  projecting 
five  inches  on  each  side  of  the  curb  and  shall  have  concrete 


VITRIFIED    PAVING    BRICK.  93 


five  inches  wide  on  both  sides  to  within  eight  inches  of  the 
top  of  the  pavement. 

The  price  bid  for  marginal  curb  per  lineal  foot  will  include 
the  curb  set  complete  together  with  the  excavation  outside 
the  face. 

VITRIFIED    BRICK   WEARING    SURFACE. 

Upon  the  foundation  shall  be  spread  about  one  inch  of  Wearing 
coarse  screened  sand,  upon  which  shall  be  laid,  as  hereinafter  Surface. 
specified,  the  vitrified  paving  brick. 

The  bricks  shall  not  be  less  than  eight  inches  nor  more 
than  ten  inches  long,  not  less  than  two  and  one-half  inches 
nor  more  than  three  and  one-half  inches  wide,  not  less  than 
four  inches  nor  more  than  four  and  one-half  inches  deep,  and 
shall  have  rounded  edges  with  a  maximum  radius  of  one- 
quarter  of  an  inch.  They  shall  be  free  from  lime  or  other  im- 
purities that  will  injuriously  affect  them  when  immersed  in 
water,  uniform  in  size  and  quality,  thoroughly  burned  and  an- 
nealed, and  free  from  internal  flaws,  cracks  and  laminations. 
All  bricks  so  distorted  in  burning  or  with  such  prominent  kiln 
marks  as  to  produce  an  uneven  pavement,  will  be  rejected. 
Not  less  than  one  hundred  bricks  of  the  kind  proposed  to  be 
used  shall  be  submitted  as  samples,  and  shall  pass  the  follow- 
ing tests: 

1.  .They  shall  show  a  modulus  of  rupture  in  cross-break- 
ing of  not  less  than  two  thousand  pounds  per  square  inch. 

2.  Specimen  bricks  shall  be  placed  in  the  machine  known 
as  a  "Rattler"  twenty-eight  inches  in  diameter  and   making 
thirty  revolutions  per  minute.    The  number  of  revolutions  for 
a  standard  test  shall  be  eighteen  hundred,  and  if  the  loss  of 
weight  by  abrasion  exceeds  25  per  cent  of  the  original  weight 
of  the  bricks,  then  they  shall  be  rejected.     An  official  test 
shall  be  the  average  of  two  of  the  above  tests. 


94  VITRIFIED    PAVING    BRICK. 


3.  They  shall  not  absorb  more  than  2  per  cent  of  their 
own  weight  of  water  after  being  immersed  in  water  for  forty- 
eight  hours;  provided,  however,  that  an  absorption  of  not  ex- 
ceeding 4  per  cent  may  be  allowed,  in  case  the  brick  will  show 
a  loss  of  weight  by  abrasion  of  not  over  20  per  cent  of  the 
original  weight  of  the  brick.  The  absorption  test  shall  be 
made  on  bricks  that  have  been  broken  and  passed  through 
the  "Rattler." 

After  the  surface  of  the  sand  has  been  made  smooth,  ex- 
actly parallel  to  the  desired  surface  of  the  street  after  com- 
pletion, and  uniformly  dense,  the  bricks  shall  be  laid  upon  it. 
They  shall  be  set  on  edge,  in  straight  courses,  as  closely  and 
compactly  as  possible  and  at  right  angles  to  the  line  of  the 
work,  except  at  street  intersections,  where  they  are  to  be  laid 
as  the  Street  Commissioner  shall  direct.  All  joints  shall  be 
broken  by  a  lap  of  at  least  two  inches,  and  no  bats  or  broken 
bricks  will  be  allowed,  except  at  the  ends  of  the  work,  for  the 
purpose  of  breaking  joints  or  making  closures,  and  in  no  case 
shall  a  bat  less  than  three  inches  long  be  used. 

After  the  bricks  are  laid  they  shall  be  surfaced  and  bedded 
by  a  thorough  rolling  with  a  steam  roller,  weighing  not  less 
than  three  nor  more  than  six  tons,  and  the  pavement  shall, 
when  completed,  conform  accurately  to  the  grade  and  cross 
section  of  the  roadway.  Wherever  a  roller  can  not  be  used, 
the  pavement  shall  be  rammed  with  a  paver's  rammer,  weigh- 
ing not  less  than  seventy-five  pounds.  If  after  rolling  or  ram- 
ming, any  bricks  are  found  to  be  slightly  above  or  below  the 
surface  of  the  pavement,  they  shall  be  carefully  adjusted,  so 
that  when  the  grout,  hereinafter  described,  is  put  in  place, 
there  will  be  no  unevenness  in  the  pavement.  An  expansion 
joint  one  inch  wide  shall  be  placed  on  each  side  of  the  road- 
way against  the  curb  or  outer  edge  of  the  gutter.  This  joint 
shall  be  about  four  inches  deep  and  shall  be  filled  with  pitch 


VITRIFIED    PAVING    BRICK.  95 


heated  to  a  temperature  of  three  hundred  degrees  Fahrenheit, 
to  within  one-half  inch  of  the  surface  of  the  pavement.  The 
grout  shall  consist  of  one  part  of  Portland  cement  and  one 
part  of  sand  mixed  with  enough  water  to  make  it  sufficiently 
fluid,  when  properly  stirred,  to  completely  fill  the  joints  in 
the  pavement.  The  cement  and  sand  shall  be  thoroughly 
mixed  dry  until  no  streakiness  remains  in  the  mixture  and  in 
such  quantities  as  may  be  desired.  Not  more  than  two  ordi- 
nary water  buckets  full  of  this  dry  mixture  shall  be  wet  at 
one  time.  From  the  time  water  is  added  to  the  cement  and 
sand  until  the  grout  is  deposited  on  the  street,  the  mixture 
shall  be  constantly  stirred  in  order  to  prevent  a  separation 
of  the  sand  and  cement.  As  soon  as  the  grout  is  transferred 
to  the  pavement,  it  shall  be  rapidly  swept  into  the  joints  and 
the  grouting  shall  not  be  considered  as  completed  until-  the 
joints  are  completely  filled.  After  the  grout  has  been  poured 
and  before  it  has  set,  the  contractor  shall  carefully  inspect 
the  surface  of  the  pavement  and  correct  any  irregularities 
that  have  not  been  previously  discovered,  whereupon  a  thin 
layer  of  clean,  coarse  sand  shall  be  spread  over  the  pavement. 
The  newly  finished  work  shall  then  be  protected  by  substan- 
tial barricades,  and  if  deemed  necessary,  by  watchmen  to 
guard  the  barricades  for  a  period  of  seven  days  after  the 
grout  is  applied. 

GUARANTEE. 

The  said part of  the  first 

part  hereby  expressly  guarantee to  maintain      Guarantee. 

in  good  order,  the  grade  and  surface  of  all  the  aforesaid 
work  of  improvement  and  the  materials  used  in  connection 
therewith,  for  a  term  of  five  years  throughout,  commencing 

on  the  date  of  acceptance  of  the  work,  and  bind 

heirs,  executors,  administrators,  successors  or  assigns  to  make 


96  VITRIFIED    PAVING    BRICK. 


all  repairs,  which  may  from  any  imperfections  in  said  work  or 
materials,  or  from  any  rotting,  crumbling  or  disintegration  of 
the  materials,  become  necessary  within  that  time,  or  if  the 
surface  of  the  pavement  shall  have  any  cracks,  bunches,  holes 
or  depressions  that  shall  measure  more  than  one-half  inch 
from  the  under  side  of  a  straight  edge  four  feet  long,  laid  on 
the  surface,  the  part.,  of  the  first  part  shall,  whenever  noti- 
fied by  the  Street  Commissioner  that  repairs  are  required,  at 

once  make  such  repairs  at own  expense.  And  if 

they  are  not  made  within  five  days  after  written  notice  is 
given  by  the  Street  Commissioner,  then  he  shall  have  the 
right  to  cause  such  repairs  to  be  made  and  the  cost  thereof 
may  be  recovered  by  the  city  upon  the  bond  given  to  secure 
the  faithful  performance  of  the  contract  let  hereunder,  by  ap- 
propriate action  in  any  court  of  competent  jurisdiction. 

And  it  is  further  agreed  in  addition  to  the  above  that  if 
during  the  first  year  of  the  term  of  guarantee,  repairs  are  not 
made  as  directed,  after  written  notice  is  given  by  the  Street 
Commissioner,  then  he  shall  have  the  right  to  cause  such  re- 
pairs to  be  made  and  the  whole  cost  thereof  shall  be  paid  out 

of  the  special  fund  of  $200.00,  which  the  part of  the  first 

part  ha.-...  paid  into  the  treasury  before  executing  this  con- 
tract, in  accordance  with  Section  1991  of  "The  Revised  Code 
of  St.  Louis."  And  this  special  fund  shall  be  kept  up  to  the 
full  amount  of  Two  Hundred  Dollars,  which  amount  will  be 
finally  repaid  in  the  manner  set  forth  in  Sections  1992  and 
1993  of  "The  Revised  Code  of  St.  Louis." 

At  the  end  of  the  five  year  period,  the  Street  Commission- 
er will  determine  whether  or  not  the  foundation  is  sound  and 
the  entire  wearing  surface  of  the  roadway  is  in  a  reasonably 
smooth  condition  and  is  free  from  signs  of  disintegration. 
The  principal  and securities  under 


VITRIFIED    PAVING    BRICK.  97 


this  contract  shall  not  be  discharged  from  liability  on  their 
bond  hereunder,  until  the  Street  Commissioner  shall  so  de- 
termine and  certify  thereto  in  writing  to  the  principal  under 
this  contract.     And  it  is  further  expressly  agreed,  that  if  at 
any  time  during  the  term  for  which  the  contract  for  guaran- 
tee is  in  force,  the  pavement  or  any  part  thereof  does  not  meet 
the   requirements   above   specified,   then   the   Street   Commis- 
sioner may,  with  the  approval  of  the  Board  of  Public  Improve- 
ments and  of  the  Mayor,  so  notify  the  contractor,  and  the  con- 
tractor shall  within  three  months  after  receiving  such  notice, 
totally  repair  or  reconstruct  the  whole  or  such  part  of  the 
pavement,  as  does  not  meet  the  requirements,  with  the  same 
kind  of  material  as  heretofore  applied,  or  with  some  other 
material  approved  by  the  Board  of  Public  Improvements.  And 
if  the  contractor  fails  to  so  totally  repair  or  reconstruct  the 
pavement  within  three  months  after  having  been  notified,  the 
Board  of  Public  Improvements  may,  with  the  approval  of  the 
Mayor,  cancel  the  contract  without  thereby  discharging  the 
liability  of  the  contractor  and  sureties,  and  relet  the  work  of 
such  total  repairing  or  reconstructing  and  the  cost  thereof 
shall  be  paid  by  the  city  and  the  amount  collected  by  suit 
from  the  contractor  and  the  sureties.    And  it  is  further  agreed 
that  whenever  any  repairs  of  the  pavement  are  made  neces- 
sary from  the  construction  of  sewers,  the  laying  of  pipes,  or 
telegraph  wires,  or  from  any  other  disturbance  of  the  same, 
by  parties  acting  under  permits  issued  by  the  city,  the  con- 
tractor shall,  on  notification   from  the   Street  Commissioner, 
in  all  cases   (except  where  the  party  causing  the  disturbance 
is  required  to  restore  the  pavement),  at  once  make  all  neces- 
sary repairs  in  conformity  with  the  specifications  under  which 
the  pavement  was  constructed.     The  cost  of  all  such  repairs, 
when  done  by  the  contractor,  exclusive  of  trenching  and  back- 


98  VITRIFIED    PAVING    BRICK. 


filling,  which  shall  be  done  by  the  parties  who  hold  the  per- 
mits, and  in  the  same  manner  as  now  required  by  existing 
ordinances,  shall  be  paid  for  at  the  rate  of  Three  Dollars 
($3.00)  per  square  yard,  provided,  however,  that  no  single 
cut  will  be  repaired  for  less  than  Ten  Dollars  ($10.00),  and 
the  measurements  thereof,  together  with  the  amount  due  the 
contractor  therefor,  shall  be  certified  to  by  the  Street  Com- 
missioner, and  shall  be  paid  out  of  the  fund  ''Street  Repairs — 
Reconstructed  Streets,"  and  the  amount  shall  be  certified  by 
the  Street  Commissioner  to  the  Auditor,  who  shall  reimburse 
by  transfer  the  aforesaid  fund  from  the  funds  of  the  proper 
department,  if  the  repairs  were  made  necessary  by  the  con- 
struction of  any  public  improvement;  and  out  of  the  funds  to 
be  deposited  by  persons  taking  permits  for  opening  the  street 
before  such  permits  were  granted,  if  the  repairs  were  made 
necessary  by  work  done  thereunder.  And  it  is  agreed  that 
the  contractor  shall  have  the  right  to  make  all  repairs  (ex- 
cept where  the  party  causing  the  disturbance  is  required  to 
restore  the  pavement),  which  become  necessary  by  the  con- 
struction of  any  public  improvements  or  work  done  by  private 
parties  under  permits  issued  and  granted  by  the  city  on  the 
basis  of  compensation  aforesaid;  provided,  however,  that  it  is 
furthermore  covenanted  and  agreed  that  this  contract  shall 
not  be  affected,  impaired  or  avoided,  and  that  no  claim  or 
compensation  for  damages  shall  be  presented  by  or  allowed 
the  contractor  for  or  on  account  of  a  disturbance  or  tearing 
up  of  the  street  by  the  City  of  St.  Louis  or  by  any  contractor 
by  it  employed,  or  by  the  grantee  of  any  franchise  now  or 
hereafter  given  and  granted  by  the  city  for  laying  conduits, 
street  railway  tracks,  gas  pipe  or  wires  of  any  character  upon, 
in  or  under  said  street. 


VITRIFIED    PAVING    BRICK.  99 


GENERAL  STIPULATIONS. 

IT    IS    FURTHER    EXPRESSLY    AGREED,    between    the      General 
parties  hereto  that  this  contract  is  made  subject  to  the  con-      Stipulations. 
ditions  and  sipulations  which  follow: 

1.  The  first  party  shall  not  assign  or  transfer  this  con- 
tract or  sub-let  any  of  the  work  embraced  in  it. 

2.  The  first  party  shall  commence  the  work  at  such  points 
as  the  Street  Commissioner  may  direct,  and  conform  to  his 
directions  as  to  the  order  of  time  in  which  the  different  parts 
of  the  work  shall  be  done,  as  well  as  to  all  his  instructions  as 
to  the  workmanship,  character  of  the  work  and  quality  of  the 
materials. 

It  being  expressly  understood  that  the  work  is  to  be  prose-- 
cuted  in  sections  of  not  less  than  the  space  between  any  two 
intersecting  streets  and  that  the  provisions  of  stipulation  10, 
relative  to  hauling,  inspection,  removal  and  piling  of  material 
shall  apply  to  the  work  on  each  of  said  sections  on  the  whole 
line  of  the  work. 

3.  Any  work  not  herein  specified,  which  may  be   fairly 
implied  as  included  in  this  contract,  of  which  the  Street  Com- 
missioner shall  judge,  shall  be  done  by  the  first  party  without 
extra  charge. 

4.  The  first  party  upon  being  so  directed  by  the  Street 
Commissioner,  shall  remove  or  reconstruct,  or  make  good  at 
his  own  cost,  any  work  which  the  latter  shall  decide  to  be  de- 
fectively executed;    and  any  omission  to  condemn  any  work 
at  the  time  of  its  construction  shall  not  be  construed  as  an 
acceptance  of  any  defective  work,  but  the  first  party  will  be 
required  to  correct  any  imperfect  work  whenever  discovered 
before  final  acceptance  of  the  work. 

5.  The  first  party  will  be  required  to  observe  all  city  or- 
dinances in   relation  to  obstructing  streets,  maintaining  sig- 


100  VITRIFIED    PAVING    BRICK. 


nals,  keeping  open  passage  ways  and  protecting  the  same 
where  exposed,  and  generally  to  obey  all  laws  and  ordinances 
controlling  or  limiting  those  engaged  on  the  work,  and  the 
said  first  party,  contractor,  hereby  expressly  binds  himself 
to  indemnify  and  save  harmless  the  City  of  St.  Louis  from 
all  suits  or  actions  of  every  name  and  description,  brought 
against  the  said  city  for  or  on  account  of  any  injuries  or  dam- 
ages received  or  sustained  by  any  party  or  parties  by  or  from 
the  acts  of  said  contractor,  or  his  servants  or  agents  in  doing 
the  work  herein  contracted  for,  or  by  or  in  consequence  of 
any  negligence  in  guarding  the  same,  or  in  any  improper  ma- 
terials used  in  its  construction,  or  by  or  on  account  of  any  act 
or  omission  of  the  said  contractor,  or  his  servants  or  agents. 

6.  To  prevent  all  disputes  or  litigation,  it  is  further  agreed 
by  the  parties  hereto,  that  the  Street  Commissioner  shall  in 
all  cases  determine  the  amount  or  quality  of  the  several  kinds 
of  the  work  which  are  to  be  paid  for  under  this  contract,  and 
he  shall  decide  all  questions  which  may  arise  relative  to  the 
execution  of  this  contract  on  the  part  of  the  contractor,  and 
his  estimates  and  decisions  shall  be  final  and  conclusive. 

7.  This  contract  is  entered  into  subject  to  the  approval 
or  rejection  of  the  council,  and  subject  to  the  City  Charter, 
and  ordinances  in  general,  and  in  particular  to  the  following 
provisions  of  Article   6,   Section   28,  of  said  Charter,   and   of 
Sections  1921  to  1932,  all  inclusive  of  "The  Revised  Code  of 
St.  Louis,"  all  of  which  by  this  reference  are  made  parts  here- 
of, as  if  here  fully  set  forth: 

a.  The  aggregate  payments  under  this  contract  shall  be 

limited  by  the  appropriation  contained  in  Ordinance  No 

authorizing  the  work  to  be  done. 

b.  "On  ten  days'  notice,  the  work  under  said  contract  may, 
without  cost  to  or  claim  against  the  City  of  St.  Louis,  be  sus- 
pended by  the  Board  of  Public  Improvements,  with  the  ap- 


VITRIFIED    PAVING    BRICK.  101 


proval  of  the  Mayor,  for  want  of  means  or  other  substantial 
cause." 

8.  The  Street  Commissioner  shall  have  the  right  to  make 
alterations  in  the  line,  grade,  plan,  form  or  dimensions  of  the 
work  herein   contemplated,   either  before   or   after  the   com- 
mencement  of   the   work.     If   such   alterations   diminish   the 
quantity  of  work  to  be  done,  they  shall  not  constitute  a  claim 
for  damages  or  for  anticipated  profits  on  the  work  dispensed 
with;  if  they  increase  the  amount  of  work,  such  increase  shall 
be  paid  for  according  to  the  quantity  done,  and  at  the  price 
or  prices  stipulated  for  such  work  in  this  contract. 

9.  The  first  party  shall  not  be  entitled  to  any  claim  for 
damages  for  any  hindrance  or  delay  from  any  cause  whatever, 
in  the  progress  of  the  work,  or  any  portion  thereof;  but  such 
hindrance  may  entitle  said  first  party  to  an  extension  of  the 
time  for  completing  this  contract  sufficient  to  compensate  for 
the  detention,  the  same  to  be  determined  by  the  Street  Com- 
missioner, provided  he  shall  have  immediate  notice  in  writing 
of  the  cause  of  detention. 

And  it  is  expressly  understood  that  the  city  or  any  corpora- 
tion or  individual  holding  franchises  under  it  may  enter  upon 
the  work  during  its  progress  and  adjust  their  tracks,  poles, 
manhole  covers,  inlets,  etc.,  so  as  to  meet  the  new  conditions 
caused  by  the  work. 

10.  The  work  embraced  in  this  contract  shall  be  begun 
within  one  week  after  written  notice  to  do  so  shall  have  been 
given  to  the  contractor  by  the  Street  Commissioner,  and  car- 
ried on  regularly  and  uninterruptedly  thereafter   (unless  the 
said   Commissioner  shall  otherwise,  in  writing,   specially  di- 
rect), with  such  a  force  as  to  insure  its  full  completion  with- 
in  thereafter,  unless  the  time  shall 

have  been  extended  by  the  Street  Commissioner  as  aforesaid 


102  VITRIFIED    PAVING    BRICK. 

and  then  within  said  period  of plus  the  additional 

time  allowed  by  said  Commissioner  the  time  of  beginning, 
rate  of  progress  and  time  of  completion  being  essential  con- 
ditions of  this  contract.  And  if  the  contractor  shall  fail  to 
complete  the  work  by  the  time  above  specified,  the  sum  of 
five  dollars  per  day  for  the  first  ten  days  and  the  sum  of  ten 
dollars  per  day  for  each  and  every  day  thereafter  until  such 
completion,  shall  be  deducted  from  the  moneys  payable  under 
this  contract. 

All  materials  to  be  used  in  the  work  before  they  are  laid 
will  be  carefully  inspected  and  all  rejected  material  shall  be 
immediately  removed  by  the  contractor  from  the  work.  The 
contractor  will  be  required  to  pile  his  material,  so  that  it  will 
not  be  within  three  feet  of  any  fire  hydrant,  and  if  any  of  it 
is  placed  upon  the  sidewalk  sufficient  passageway  must  be 
provided  and  also  free  access  from  the  roadway  to  each  house 
on  the  line  of  the  street. 

The  contractor  shall  furnish  and  shall  have  on  the  line  of 
the  work  a  complete  and  sufficient  plant  of  tools,  rollers,  carts, 
etc.,  so  as  to  carry  on  the  work  expeditiously  and  in  a  work- 
manlike manner. 

The  contractor  will  be  required  to  furnish  such  laborers 
as  may  be  necessary  to  aid  the  inspector  in  the  examination 
and  culling  of  material. 

11.  And  if  the  contractor  shall  assign  this  contract  or 
abandon  the  work,  or  shall  neglect  or  refuse  to  comply  with 
the  specifications  or  stipulations  herein  contained,  or  if  at 
any  time  the  Street  Commissioner  shall  be  of  the  opinion  that 
the  work  is  unnecessarily  delayed  and  will  not  be  finished 
within  the  prescribed  time,  he  shall  notify  the  contractor  in 
writing  to  that  effect;  and  if  the  contractor  shall  not  within 
five  days  thereafter  take  such  measures  as  will,  in  the  judg- 
ment of  the  said  Commissioner,  insure  the  satisfactory  com- 


VITRIFIED    PAVING    BRICK.  103 


pletion  of  the  work,  the  Board  of  Public  Improvements  shall 
have  the  right,  with  the  consent  of  the  Mayor,  to  annul  and 
cancel  this  contract  and  to  relet  the  work,  or  any  part  there- 
of, and  such  annulment  shall  not  entitle  the  contractor  to 
any  claim  for  damages  on  account  thereof,  nor  shall  it  affect 
the  right  of  the  city  to  recover  damages  which  may  arise 
from  such  failure. 

NOTE: — The  word  "contractor"  wherever  used  in  this  in- 
strument, means  the  first  party  to  this  agreement,  or  the 
legal  representative  of  such  party;  and  the  words  "Street 
Commissioner,"  refer  to  the  person  holding  that  office  for  the 
time  being,  and  to  his  properly  authorized  agents,  limited  by 
the  particular  duties  entrusted  to  them. 

PAYMENTS. 

In  consideration  of  the  completion  by  the  said  first  party  Payments. 
of  all  the  work  embraced  in  this  agreement  in  conformity 
with  the  specifications  and  stipulations  herein  contained,  the 
party  of  the  second  part  hereby  agrees  to  pay  to  the  said  first 
party  the  following  prices,  by  issuing  special  tax  bills  as  here- 
inafter provided: 

For  grading  and  preparing  the  roadbed  for  the  superstruc- 
ture, per  cubic  yard cents ; 

For  granite  curbing,  furnished  and  set  complete,  per  lineal 
foot Dollars  ($ ) ; 

For  marginal  curbing,  furnished  and  set  complete,  per  line- 
al foot cents ; 

For  vitrified  brick  pavement,  including  concrete  founda- 
tion, furnished  and  laid  complete,  per  square  yard 

Dollars  ($ ) ; 

For  macadam,  per  cubic  yard 

Dollars   ($ ). 

When  all  thfe  work  embraced  in  this  contract  is  fully  com- 


104  VITRIFIED    PAVING    BRICK. 


pleted,  in  accordance  with  the  specifications  and  stipulations 
of  this  agreement,  without  regard  to  the  provisions  of  guar- 
antee and  accepted  by  the  Street  Commissioner,  said  Commis- 
sioner shall  cause  a  careful  measurement  of  said  work  to  be 
made,  arid  certify  the  same  to  the  President  of  the  Board  of 
Public  Improvements,  who  shall  compute  the  cost  thereof  ac- 
cording to  the  terms  and  prices  of  this  agreement  and  levy 
and  assess  the  same  as  a  special  tax  against  each  lot  of 
ground  chargeable  therewith  in  the  name^  of  the  owners 
thereof. 

The  lots  of  grounds  chargeable  aforesaid  are  those  em- 
braced within  a  district  defined  and  bounded  in  Section  14 
of  Article  6  of  the  Charter  of  the  City  of  St.  Louis. 

One-fourth  of  said  cost  shall  be  levied  and  assessed  as  a 
special  tax  upon  all  the  property  fronting  upon  or  adjoining 
the  improvement  hereinbefore  described,  in  the  proportion 
that  the  frontage  of  each  lot,  so  fronting  or  adjoining  bears 
to  the  total  aggregate  of  frontage  of  all  lots  or  parcels  of 
ground  upon  or  adjoining  the  improvement,  and  the  remain- 
ing three-fourths  of  the  cost  shall  be  levied  and  assessed  as 
a  special  tax  upon  all  the  property  in  the  area  district  defined 
and  bounded  in  said  Section  14  of  Article  6,  of  the  Charter 
of  the  City  of  St.  Louis,  in  the  proportion  that  the  area  of 
each  lot  or  parcel  of  ground,  or  the  part  of  such  parcel  of 
ground,  lying  within  said  district,  bears  to  the  total  area  of 
the  district,  exclusive  of  streets  and  alleys 


Each  of  said  special  tax  bills  so  to  be  issued  shall  be  di- 
vided into equal  parts,  as  provided  by  the  ordi- 
nance authorizing  said  improvement,  the  first  installment  to 
become  due  and  payable  thirty  days  after  due  notice  of  the 
issuance  thereof,  without  interest,  and  the  remaining  install- 
ments to  become  due  and  payable  at  intervals  of  one  year 


VITRIFIED    PAVING    BRICK.  105 


thereafter,  provided,  however,  that  the  owner  or  any  person 
interested  in  the  property  charged  with  any  tax  bill  may  pay 
the  same  in  full  at  any  time  within  thirty  days  after  such 
notice  without  interest,  and  may  pay  the  same  in  full  at  any 
time  by  paying  interest  thereon  as  follows: 

If  paid  at  or  before  maturity,  and  more  than  thirty  days 
after  notice  as  aforesaid,  at  the  rate  of  6  per  cent  per  annum 
from  date  of  notice  to  date  of  payment;  if  paid  after  maturity, 
at  the  rate  of  6  per  cent  per  annum  from  date  of  notice  to 
date  of  maturity,  and  at  the  rate  of  8  per  cent  per  annum 
from  date  of  maturity  to  date  of  payment.  All  interest  to  be 
payable  annually  from  date  of  notice  as  aforesaid,  and  if  any 
installment  or  equal  part,  or  any  interest  on  any  installment 
be  not  paid  when  due,  then  at  the  option  of  the  holder  thereof 
all  remaining  installments  shall  become  due  and  collectible 
with  interest  thereon  as  above  provided.  And  said  special 
tax  bills  shall  be  made  out  by  the  President  of  the  Board  of 
Public  Improvements  and  by  him  registered  in  his  office  in 
full,  and  certified  and  delivered  to  the  Comptroller  and  his 
receipt  taken  therefor,  and  by  him  registered  and  counter- 
signed^ and  delivered  to  the  party  of  the  first  part,  in  whose 
favor  they  are  issued  for  collection,  and  his  receipt  taken  in 
full  of  all  claims  against  the  city  on  account  of  said  work. 

PROVIDED,  That  nothing  herein  contained  shall  be  so 
construed  to  affect  the  right  of  the  city,  hereby  reserved,  to 
reject  the  whole  or  any  portion  of  the  work  aforesaid,  should 
the  measurement  or  computation  before  mentioned  be  found 
or  known  to  be  improperly  made,  or  to  be  inconsistent  with 
the  terms  of  this  agreement. 

The  said  

as  Principal  and 

.  and 


106  VITRIFIED    PAVING    BRICK. 

as  Securities,  hereby  bind  themselves  and  their  respective 
heirs,  executors,  administrators,  successors  or  assigns,  unto 

the  said  City  of  St.  Louis  in  the  penal  sum  of 

Dollars,    lawful    money   of   the    United 

States,  conditioned  that  in  the  event  of  the  said 

shall  faithfully  and  properly  per- 
form the  foregoing  contract,  not  only  as  to  the  work  of  con- 
struction, but  also  as  to  the  repair  and  guarantee  thereof,  ac- 
cording to  all  the  terms  thereof,  and  shall,  from  time  to  time, 
as  soon  as  the  work  contemplated  by  said  contract  is  com- 
pleted, pay  to  the  proper  parties  all  amounts  due  for  material 
and  labor  used  and  employed  in  the  performance  thereof,  then 
this  obligation  to  be  void,  otherwise  in  full  force  and  effect. 
Said  bond  may  be  sued  on  at  the  instance  of  any  material 
man,  laboring  man,  or  mechanic,  in  the  name  of  the  City  oi 
St.  Louis,  to  the  use  of  such  material  man,  laboring  man  or 
mechanic,  for  any  breach  of  the  conditions  hereof;  provided, 
that  no  suit  shall  be  instituted  after  the  expiration  of  ninety 
days  from  the  completion  of  any  work  under  the  above  con- 
tract. 

IN  WITNESS  WHEREOF,  the  said 

as  principal  and   

and  as  securities, 

parties  of  the  first  part,  have  hereunto  set  their  hands  and 
seals  respectively  and  the  City  of  St.  Louis,  party  of  the  sec- 
ond part,  acting  by  and  through  the  Board  of  Public  Improve- 
ments aforesaid  have  subscribed  these  presents,  the  day  and 
year  first  above  written. 

WITNESS: 

(Seal) 

(Seal) 

(Seal) 


VITRIFIED    PAVING    BRICK.  107 

(Seal) 

(Seal) 

(Seal) 

The  City  of  St.  Louis,  by 

President  Board  of  Public  Improvements. 

Countersigned : 

Comptroller. 
CITY  COUNSELOR'S  OFFICE. 

St.    Louis, 190 .. 

The  foregoing  Agreement  and  Bond  are  in  due  form  accord- 
ing to  law. 

City  Counselor. 
MAYOR'S  OFFICF. 

St.  Louis, 190 .. 

I  hereby  approve  of  the  securities  to  the  foregoing  Contract 
and  Bond. 

Mayor. 

N.  P.  B.  M.  A.  SPECIFICATIONS  FOR  LAYING  PAVING 

BRICK. 

The  following  specifications  for  laying  brick  pavements  is 
recommended  by  the  National  Paving  Brick  Manufacturers'  ~  ^  J^! 
Association.  As  this  body  represents  the  leading  makers  of 
paving  brick  throughout  the  United  States,  it  is  the  result  of 
a  most  broad  and  thorough  experience  in  the  use  and  abuse 
of  vitrified  brick  pavements,  and  is  worthy  of  careful  consid- 
eration. It  covers  both  the  use  of  concrete  and  No.  2  brick 
for  the  foundation: 


roller.    Then  you  have  different  characters  of  solidity,  which 
are  objectionable  and  detrimental  to  good  work. 

The  prime  reasons  for  not  using  a  roller  weighing  more 
than  eight  (8)  tons  is  that  they  are  too  cumbersome  and  un- 
wieldly  and  very  slow  moving,  while  with  a  lighter  and  quicker 


VITRIFIED    PAVING    BRICK.  109 


moving  one  you  pass  many  times  over  the  subgrade  and  get 
better  results  in  having  your  subgrade  more  uniformly  com- 
pacted. 

The  filling  with  loose  earth  of  portions  of  the  work  that  is 
below  grade  will  be  found  necessary  very  often  if  an  attempt 
is  made  to  plow  too  close  to  the  grade  line,  then  the  lighter 
roller  is  found  more  effective  in  bringing  such  places  to  the 
same  density  as  the  undisturbed  portion. 

When  embankment  is  necessary  to  bring  the  street  to  the 
required  grade  line,  it  is  very  obvious  that  the  earth  should 
be  deposited  in  equal  layers  of  not  more  than  eight  (8)  inches 
thick,  and  each  layer  thoroughly  rolled.  A  six  or  eight  ton,  or 
even  a  heavier  roller,  will  have  little  effect  in  compression  be- 
low eight  inches,  and  all  embankments  should  be  compacted 
as  thoroughly  as  possible  before  applying  the  superstructure; 
for  earth  once  disturbed  and  removed  from  its  natural  bed 
takes  a  long  time  to  acquire  its  original  solidity,  the  scientific 
reason  for  which  would  take  too  much  space  and  time  to  en- 
ter upon  here. 

Under-drainage  is  not  absolutely  essential,  but  in  wet  and 
spouty  under  stratum  much  is  added  to  the  durability  of  the 
structure  by  keeping  the  sub-foundation  dry,  and  under  fore- 
going wet  conditions  under-drainage  is  the  only  way  to  ac- 
complish the  best  results. 

CURBING.— Stone  curbing  should  all  be  hauled  and  dis-     Curbjn 
tributed  and  set  before  the  grading  is  finished,  and  may  then 
be  used  as  a  guide  to  finish  the  subgrade. 

It  should  range  in  thickness  from  four  (4)  to  six  (6) 
inches,  twenty  (20)  to  thirty-six  (36)  inches  wide,  the  busi- 
ness and  street  traffic  governing  the  same,  and  lengths  not 
shorter  than  four  (4)  feet,  except  at  closures.  Neatly  dressed 
on  top  with  a  square  or  rounded  edge,  and  four  (4)  inches 


110  VITRIFIED    PAVING    BRICK. 


down  on  the  inside.  The  outer  surface  to  be  tool-dressed  to 
the  depth  of  the  face  exposed  and  to  the  depth  of  the  thick- 
ness of  the  brick  and  sand  cushion.  If  cement  concrete  curb 
is  used,  it  should  be  completed  before  the  work  of  finishing 
the  sub-grade  begins. 

Curb  corners  of  streets  and  alleys  should  be  made  circu- 
lar. 

EXTRA  MENTION.— If  concrete  curb  and  gutter  is  used, 
it  must  be  placed  in  position  before  any  of  the  other  work  is 
commenced,  except  possibly,  some  of  the  heavier  grading,  and 
it  is  essential,  if  natural  stone  curb  is  used,  to  have  it  all  in 
place  before  any  portion  of  the  grading  is  finished,  for  the 
reason  that,  after  you  have  finished  a  subgrade  and  given  it 
the  proper  contour  and  surface  it  should  never  be  disturbed 
by  unnecessary  wheelage,  and  nothing  destroys  it  so  effectu- 
ally as  hauling  heavy  stone  curb  over  it;  and  in  renewing 
these  broken  places  they  are  rarely  returned  to  the  original 
conditions. 

The  curb  should  all  be  set  before  the  finishing  of  the  sub- 
grade  begins,  if  for  no  other  reason  than  that  it  affords  the 
very  best  guide  for  the  said  finishing. 

MARGINAL  CURB.— Should  always  be  of  a  hard  and  dur- 
able character  of  stone,  and  from  fourteen  (14)  to  eighteen 
(18)  inches  deep,  dressed  on  top,  and  five  (5)  inches  down 
on  the  face  next  to  the  brick.  Set  to  accurately  fit  the  cur- 
vature of  the  cross-section  of  the  street  on  six  (6)  inches  of 
concrete  and  backed  up  with  the  same  within  six  (6)  inches 
of  the  top. 

EXTRA  MENTION.— Marginal  curb  should  always  be  of 
a  hard  and  durable  character  of  stone  (hard  wood  is  better 
than  soft  stone),  and  set  on  and  backed  up  with  a  good  Port- 
land cement  concrete,  mixed  in  the  proportion  of  one  to  two 
to  four. 


VITRIFIED    PAVING    BRICK.  Ill 


Marginal  curb  is  as  a  rule  used  to  sustain  a  paved  street 
against  one  that  is  unpaved,  therefore,  the  reason  it  should  be 
well  and  properly  set,  and  unless  it  is,  the  impact  of  the  wheel- 
age  in  passing  from  the  unpaved  to  the  paved  street  will  soon 
drive  it  down  and  loosen  it  if  not  firmly  and  securely  set,  and 
in  a  short  time  the  pavement  begins  to  break  and  give  way 
and  will  continue  to  do  so  for  quite  a  distance  into  the  inter- 
section. 

Even  with  the  marginal  curb  set  in  the  above  manner  there 
should  be  a  margin  of  crushed  stone  or  clean  gravel  to  the 
width  of  three  or  four  feet  and  eight  (8)  or  ten  (10)  inches 
deep  spanning  the  width  of  the  opposing  unpaved  street  and 
tamped  firmly  against  the  marginal  curb.  With  these  precau- 
tions you  will  avoid  the  rapid  destruction  of  the  margin  of 
your  paved  streets. 

FOUNDATION. — Note:  It  has  been  fully  demonstrated,  Foundation. 
as  shown  by  the  report  of  Prof.  Baker  (a  copy  of  which  may 
be  had  upon  application),  that  a  foundation  constructed  of 
No.  2  Paving  Block  possesses  greater  strength  than  a  six- 
inch  concrete  base.  It  affords  the  greatest  possible  sanitation 
and  it  is  believed  by  many  engineers  that  it  affords  a  better 
foundation  even  than  concrete.  Other  physical  features  af- 
forded are  favorable  to  the  No.  2  Block  foundation,  as  well  as 
the  fact  that  in  many  cases  even  a  less  cost  price  is  secured 
by  its  use.  Therefore,  either  the  No.  2  Paving  Block  founda- 
tion may  be  adopted,  or  concrete  foundation  as  may  be  de- 
sired. 

NO.  2  PAVING  BLOCK  FOUNDATION.— Upon  the  sub- 
grade  as  heretofore  prepared  shall  be  spread  a  base  of  sand 
two  (2)  inches  in  thickness  and  which  shall  be  brought  to  a 
perfect  grade  conforming  to  that  of  the  finished  street. 

There  shall  be  laid  flatwise  at  right  angles  with  the  street, 


112  VITRIFIED    PAVING    BRICK. 


upon  this  grade  thus  prepared,  a  layer  of  No.  2  Paving  Block 
not  less  than  three  (3)  inches  in  thickness,  the  interstices  of 
which  shall  be  filled  with  a  filler  composed  of  two  parts  of 
clean  sand  and  one  part  of  Portland  cement.  This  filler  shall 
be  prepared  and  applied  as  provided  for  in  Section  10  of  this 
direction  and  specification.  The  foundation  thus  made  should 
remain  undisturbed  at  least  thirty-six  (36)  hours  before  the 
sand  cushion  herein  provided  for  may  be  spread,  and  at  least 
ten  (10)  days  must  elapse  before  rolling  and  compacting  of 
brick  surface  is  allowed,  and  in  no  event  must  teams  be  per- 
mitted or  hauling  be  allowed  upon  this  surface  during  this 
period. 

CONCRETE  FOUNDATION. — Should  be  of  approved  qual- 
ity of  hard  rock,  free  from  all  refuse  and  foreign  matter,  with 
no  fragment  larger  than  will  pass  through  a  two  (2)  inch  ring, 
and  excluding  all  fragments  less  than  one  inch  in  their  longest 
dimensions. 

Clean,  sharp,  dry  sand  thoroughly  mixed  in  its  dry  state 
with  an  approved  brand  of  either  hydraulic  or  Portland  ce- 
ment until  the  whole  mass  shows  an  even  shade.  If  hydraulic, 
the  proportion  of  mixture  should  be  one  part  of  cement  and 
two  parts  of  sand.  If  of  Portland,  one  part  of  cement  to  three 
parts  of  sand. 

To  the  above  mixture  should  be  added  sufficient  clean 
water  to  mix  to  a  plastic  mass,  fluid  enough  to  rapidly  sub- 
side when  attempted  to  heap  into  a  cone  shape.  To  this  mix- 
ture add  four  (4)  and  six  (6)  parts,  respectively  of  damp 
crushed  stone,  or  good  gravel  carrying  sufficient  sand  to  make 
the  mixture,  and  then  turn  the  whole  mass  over  not  less  than 
three  (3)  times,  or  until  every  fragment  is  thoroughly  coated 
with  the  cement  mixture.  For  the  reception  of  this  mixture, 
the  grade  should  be  set  off  in  five-foot  squares,  with  a  stake 


VITRIFIED    PAVING    BRICK.  113 


at  each  corner.  Tops  of  each  should  be  at  the  surface  of  con- 
crete, which  must  be  tamped  until  free  mortar  appears  on  the 
surface.  Occasional  sprinkling  in  extra  hot,  dry  weather  is 
beneficial.  After  thirty-six  hours  the  cushion  sand  may  be 
spread. 

EXTRA  MENTION.— If  the  combination  of  gravel  and  sand 
is  used  the  mixture  for  natural  cement  should  be  one  (1) 
measure  of  cement  to  six  (6)  measures  of  the  mixture.  If 
Portland  cement,  one  (1)  measure  of  cement  to  eight  (8) 
measures  of  the  mixture. 

There  is  but  one  way  to  make  good  cement  mixtures,  pre- 
suming, of  course,  you  have  good  material,  and  that  is  to 
thoroughly  mix  the  dry  materials.  It  is  essential  that  the 
sand  and  cement  should  be  thoroughly  incorporated  in  their 
dry  state,  if  not  then  it  can't  be  done  after  the  water  is  ap- 
plied. In  the  first,  you  will  have  a  homogeneous  mass;  in  the 
second,  a  heterogeneous.  In  the  one  your  mixture  is  complete 
and  your  structure  is  uniform;  in  the  other,  it  varies  and 
your  structure  is  uncertain.  The  above  applies  especially  to 
platform  mixing.  In  machine  manipulation  the  dry  mixing 
isn't  so  readily  obtainable,  but  could  be  more  nearly  ap- 
proached if  greater  care  were  taken.  Thorough  mixing  in 
both  dry  and  wet  state,  with  good  material  and  proper  pro- 
portions, insures  a  good  concrete,  whether  it  be  of  crushed 
stone  or  gravel. 

SAND  CUSHION.— Sand  should  be  clean  and  free  from 
foreign  or  loamy  matter.  It  need  not  necessarily  be  sharp. 
It  should  be  two  (2)  inches  thick  before  the  compression  of  Sand  Cushion. 
the  brick  by  rolling.  The  sand  should  be  spread  by  the  aid 
of  a  template  the  whole  or  one-half  the  width  of  the  street, 
and  made  to  conform  with  the  true  curvature  of  the  street 
cross-section. 


114  VITRIFIED    PAVING    BRICK. 


EXTRA  MENTION.— The  preparation  of  the  subgrade 
having  been,  with  care,  brought  to  a  true  plane  as  to  curva- 
ture and  grade,  and  to  a  uniform  thickness,  the  work  is 
ready  for  the  cushion  for  the  brick,  for  which  any  good,  clean 
sand  may  be  used  whether  it  be  sharp  or  spherical,  but  it  is 
next  to  the  impossible  to  spread  it  satisfactorily  with  a  tem- 
plate or  in  any  other  manner  when  it  is  wet,  and  if  you  insist 
on  your  pavement  maintaining  its  symmetrical  form  the  sand 
must  be  evenly  spread ;  and  there  is  but  one  method  for  doing 
this,  and  that  is  mechanically,  by  the  aid  of  a  template, 
formed  to  fit  the  curvature  of  the  street  and  armed  with  small 
metal  wheels  at  either  end,  rolling  on  the  curb  at  one  end 
and  on  a  4x4-inch  scantling  laid  lengthwise  through  the  center 
of  the  street  at  the  other. 

If  the  roadway  of  the  street  isn't  to  exceed  twenty-five  (25) 
feet  in  the  width  or  less,  the  template  can  be  made  to  span 
the  entire  width,  both  ends  rolling  on  the  curb. 

This  manner  insures  an  even  thickness  of  sand  over  the 
surface  of  the  concrete,  giving  to  each  individual  brick  a  like 
thickness  of  cushion,  so  that  when  the  brick  surface  is  rolled 
each  brick  will  present  the  same  resistance  to  the  pressure  of 
the  roller,  and  you  will  then  perforce  have  a  smooth  surface, 
otherwise  if  the  sand  is  of  uneven  thickness  the  tendency  of 
those  brick  resting  on  the  thicker  bed  of  sand  is  to  sink,  under 
the  pressure  of  the  roller,  lower  than  those  resting  on  a  thin- 
ner layer,  and  the  result  is  an  undulating  and  uneven  surface. 

BRICK.— The  brick  should  all  be  hauled  and  neatly  piled 
Brick,  within  the  curb  line  before  the  grading  is  finished,  or  if  al- 
lowed by  the  engineer,  delivered  in  wagons  and  carried  from 
the  pile  or  wagon  on  pallets  with  clamps — not  wheeled  with 
barrows.  In  hauling  from  car  no  throwing  or  dumping  is 
allowed.  They  should  be  first-class  and  thoroughly  vitrified, 


VITRIFIED    PAVING    BRICK.  115 


showing  at  least  one  fairly  straight  face;  if  the  edges  are 
rounded  the  radius  should  not  be  greater  than  3-16  of  an  inch. 
They  should  not  be  less  than  21/4x4x8,  or  more  than  31/£x4x91/£» 
inches,  free  from  cracks,  with  but  slight  lamination,  and  at 
least  one  edge  with  but  slight  kiln  marks  allowed,  and  should 
stand  the  tests  promulgated  by  the  National  Brick  Makers' 
Association. 

EXTRA  MENTION. — It  is  not  only  good  practice  to  have 
all  of  the  brick  hauled  and  distributed  just  inside  the  curb 
line  before  the  work  of  grading  begins  on  any  street  block, 
but  it  is  economy,  as  experience  has  taught  us  that  it  is  very 
expensive  to  attempt  to  get  brick  into  a  block  after  the  other 
work  has  begun.  Each  side  of  the  street  should  have  the  re- 
quired number  of  brick  neatly  ricked  up  to  lay  to  the  center 
of  the  street,  thereby  always  maintaining  the  minimum  dis- 
tance to  carry  the  brick  to  the  setter. 

In  order  to  get  the  brick  to  the  setter  with  the  least  pos- 
sible abrasion  or  injury  to  the  same,  it  is  best  to  carry  them 
on  pallets,  and  so  deposit  them  that  the  person  laying  them 
in  the  street  will  deposit  them  perfect  edge  up.  No  wheeling 
or  teaming  should  be  permitted  over  the  brick  at  any  stage 
prior  to  opening  the  same  to  the  public  . 

BRICK  LAYING.— Brick  may  be  laid  either  at  a  right  Brick  Laying. 
angle  or  an  angle  of  45  degrees  to  the  curb,  as  the  engineer 
may  direct,  and  in  either  way  the  line  or  course  of  brick  must 
be  kept  straight  or  within  a  maximum  variation  of  two  inches ; 
if  greater  than  that,  as  many  courses  as  necessary  should  be 
taken  up  and  relaid  until  the  defect  in  alignment  is  removed. 

No  parts  of  brick  should  be  allowed  in  the  pavement  ex- 
cept the  beginning  or  ending  of  courses  or  other  closures. 
The  brick  must  be  laid  with  the  best  edges  exposed  as  near  in 
contact  as  possible;  they  must  be  closely  inspected  before 


116  VITRIFIED    PAVING    BRICK. 


laying  and  also  after  laying  and  after  rolling.  All  soft  brick, 
and  those  badly  spalled  or  ill-shapen,  must  be  removed  and 
replaced  with  perfect  ones.  The  kiln-marked  ones  may  be 
turned  over,  and  if  the  reverse  edge  is  smooth  and  no  other 
faults  be  found,  they  can  remain  in  the  pavement. 

EXTRA  MENTION. — As  to  the  alignment  of  the  courses 
of  the  brick  there  is  but  little  choice,  either  way  is  admis- 
sible without  comment.  The  brick  should  be  as  nearly  in 
contact  as  it  is  possible  to  lay  them,  for  when  the  rolling  is 
in  progress,  if  there  is  appreciable  space  between  the  brick 
in  the  compression  and  bedding  into  the  cushion  sand,  the 
brick  will  have  a  tendency  to  rock,  and  instead  of  receiving 
a  flat  foundation,  as  they  should,  it  will  be  in  a  curved  form, 
made  by  the  rocking  of  the  brick  as  the  roller  passes  on  and 
off  them,  and  the  pavement  will  require  more  grout  to  fill  the 
interstices. 

It  isn't  bad  practice,  if  the  gutter  gradient  is  very  flat,  to 
lay  five  or  six  longitudinal  courses  parallel  with  the  curb,  as 
there  will  be  less  hindrance  to  the  gutter  drainage. 

ROLLING  AND  TAMPING.— After  the  brick  in  the  pave- 
Rolling  and  ment  are  inspected  and  the  surface  is  swept  clean  of  spalls, 
Tamping.  ^ney  must  be  well  rolled  with  a  five  (5)  ton  steam  roller  in 
the  following  manner:  The  brick  next  the  curb  should  be 
tamped  with  a  hand  wood  tamper  to  'the  proper  gutter  grade. 
The  rolling  will  then  commence  near  the  curb  at  a  very  slow 
pace  and  continue  back  and  forth  until  the  center  of  the  pave- 
ment is  reached,  then  pass  to  the  opposite  curb  and  repeat 
in  the  same  manner  to  the  center  of  the  street.  After  this 
first  passage  of  the  roller  the  pace  may  be  quickened  and  the 
rolling  continued  until  each  brick  is  firmly  imbedded  in  the 
sand  cushion.  The  roller  shall  then  be  started  at  the  end  of 
the  block  and  the  pavement  rolled  transversely  at  an  angle 


VITRIFIED    PAVING   BRICK.  11? 


of  45  degrees  to  curb,  repeat  the  rolling  in  like  manner  in  the 
opposite  direction.  Before  this  transverse  rolling  takes  place 
all  broken  or  injured  brick  must  be  taken  up  and  replaced 
with  perfect  ones. 

EXTRA  MENTION. — There  is  no  question  open  to  discus- 
sion as  to  the  virtue  of  a  steam  roller  on  a  brick  pavement. 
It  is  very  necessary  in  order  to  give  it  a  smooth  surface.  The 
transverse  rolling  is  very  necessary  in  order  to  remove  the 
slight  wavy  condition  of  the  surface  extending  laterally  from 
curb  to  curb,  which  will  occur  after  the  longitudinal  rolling, 
and  is  the  result  of  the  thrust  or  impact  occasioned  by  the 
propelling  power  of  the  roller.  If  the  roller  was  drawn  in- 
stead of  being  propelled  these  apparent  waves  would  not  oc- 
cur. Therefore,  the  transverse  rolling  will  practically  remove 
them.  The  longitudinal  rolling  should  always  be  from  curb 
toward  the  center.  The  curved  transverse  section  of  the 
street  has  a  tendency  to  move  the  brick  endwise  toward  the 
curb,  therefore,  under  the  pressure  of  the  roller,  if  you  start 
the  roller  in  the  middle  and  roll  toward  the  curb  the  gutter 
bricks  that  you  have  previously  tamped  to  grade  will  be  very 
much  disturbed  and  your  flow  line  will  require  retamping.  If 
it  were  practicable  to  use  the  roller  absolutely  against  the 
curb  the  rolling  might  be  done  from  the  center  to  the  curb. 

EXPANSION  CUSHION. — An  expansion  cushion  must  be 
provided  for  next  to  the  curb.     It  must  be  one  inch  or  more      Expansion 
in    thickness,    according    to    the    width   of    the    street.      This      Cushion. 
cushion  shall  be  composed  of  pitch  or  asphaltum  composition, 
filling  two-thirds  the  allotted  space,  the  remaining  top  third 
to  be  filled  with  sand. 

EXTRA  MENTION.— This  pitch  joint  next  to  and  along 
the  curb  answers  two  purposes,  it  takes  up  the  expansion  of 
the  brick  and  prevents  a  possible  cracking  of  the  pavement 


118  VITRIFIED    PAVING    BRICK. 


through  and  along  the  center  of  the  street,  which  sometimes 
occurs  if  the  ends  of  the  courses  of  the  brick  are  abutted  di- 
rectly against  the  curb,  which  acts  as  a  skewback  or  haunch 
to  the  arc  of  the  pavement,  which  is  often  strong  enough 
(especially  if  the  sidewalk  is  up  to  and  against  the  inside  of 
the  curb)  to  resist  the  force  of  expansion  in  that  direction 
and  it  will  find  relief  in  raising  the  pavement  and  the  crack- 
ing mentioned  above  may  occur.  And  again,  in  taking  up  the 
expansion  the  brick  are  kept  in  contact  with  the  sand  cushion 
below,  thereby  preventing  the  rumbling  noise  so  often  heard, 
and  occasioned  wholly  through  lack  of  contact. 

The  inch  of  sand  on  the  top  of  the  pitch  joint  has  a  ten- 
dency to  prevent  the  pitch  from  flowing,  which  it  is  likely  to 
do  in  very  hot  weather.  It  is  essential  that  the  board  occupy- 
ing the  place  to  be  filled  with  pitch  remain  in  place  until 
after  the  street  is  in  all  other  respects  finished,  but  always 
withdrawn  and  the  pitch  applied  within  thirty-six  hours  after 
the  application  of  the  cement  filler. 

THE  FILLER. — The  filler  shall  be  composed  of  one  part 
rillcr.  each  of  clean  sand  and  Portland  cement.  The  sand  should  be 
dry.  The  mixture,  not  exceeding  one-third  bushel  of  the  sand, 
together  with  a  like  amount  of  cement,  shall  be  placed  in  the 
box  and  mixed  dry,  until  the  mass  assumes  an  even  and  un- 
broken shade.  Then  water  shall  be  added,  forming  a  liquid 
mixture  of  the  consistency  of  thin  cream. 

From  the  time  the  water  is  applied  until  the  last  drop  is 
removed  and  floated  into  the  joints  of  the  brick  pavement, 
the  same  must  be  kept  in  constant  motion. 

The  mixture  shall  be  removed  from  the  box  to  the  street 
surface  with  a  scoop  shovel,  all  the  while  being  stirred  in  the 
box  as  the  same  is  being  thus  emptied.  The  box  for  this  pur- 
pose shall  be  3%  to  4  feet  long,  27  to  30  inches  wide  and  14 


VITRIFIED    PAVING    BRICK.  119 


inches  deep,  resting  on  legs  of  different  lengths,  so  that  the 
mixtures  will  readily  flow  to  the  lower  corner  of  the  box, 
which  should  be  from  8  to  10  inches  above  the  pavement.  This 
mixture,  from  the  moment  it.  touches  the  brick,  shall  be  thor- 
oughly swept  into  the  joints. 

Two  such  boxes  shall  be  provided  in  case  the  street  is 
twenty  feet  or  less  in  width;  ^exceeding  twenty  feet  in  width, 
three  boxes  should  be  used. 

The  work  of  filling  should  thus  be  carried  forward  in  line 
until  an  advance  of  fifteen  to  twenty  yards  has  been  made, 
when  the  same  force  and  appliances  shall  be  turned  back  and 
cover  the  same  space  in  like  manner,  except  to  make  the  pro- 
portions two-thirds  Portland  cement  and  one-third  sand. 

To  avoid  the  possibility  of  the  thickening  at  any  point, 
there  should  be  a  man  with  a  sprinkling  can,  the  head  per- 
forated with  small  holes,  sprinkling  gently  the  surface  ahead 
of  the  sweepers. 

Within  one-half  to  three-quarters  of  an  hour  after  this  last 
coat  is  applied  and  the  grout  between  the  joints  has  fully  sub- 
sided and  the  initial  set  is  taking  place,  the  whole  surface 
must  be  slightly  sprinkled  and  all  surplus  mixture  left  on  the 
tops  of  the  bricks  swept  into  the  joints,  bringing  them  up 
flush  and  full. 

After  the  joints  are  thus  filled  flush  with  the  top  of  the 
bricks  and  sufficient  time  for  evaporation  has  taken  place,  so 
that  the  coating  of  sand  will  not  absorb  any  moisture  from 
the  cement  mixture,  one-half  inch  of  sand  shall  be  spread 
over  the  whole  surface,  and  in  ease  the  work  is  subjected  to 
a  hot  summer  sun,  an  occasional  sprinkling,  sufficient  to  damp- 
en the  sand,  should  be  followed  for  two  or  three  days. 

EXTRA  MENTION.— Dry,  sharp  sand  for  this  mixture  is 
necessary  without  question  or  comment. 


120  VITRIFIED    PAVING   BRICK. 

The  first  application  should  be  thin  in  order  that  it  may 
flow  to  the  depth  of  the  joints  of  the  bricks,  thereby  insuring 
a'  substantial  bond,  and  should  be  kept  in  constant  motion 
while  being  applied,  otherwise  the  sand  will  settle  and  you 
will  have  water  and  cement  instead  of  water,  sand  and  cement. 
The  water  and  cement  wouldn't  be  objectionable,  but  the  sand 
by  itself  is  wholly  so. 

It  must  also  be  mixed  in  small  quantities,  as  it  is  next  to 
impossible  to  keep  the  sand  in  suspension  when  more  than  a 
common  water  pail  of  each,  sand  and  cement,  is  used,  and  un- 
less it  is  deposited  upon  the  pavement  with  the  sand  in  com- 
bination with  the  solution  you  will  get  the  cement  and  water 
in  the  lower  portion  of  the  joints  between  the  bricks  and  the 
sand  without  the  cement  in  the  upper  portion.  It  is  preferable, 
after  the  sand  and  cement  have  been  mixed  dry,  to  apply 
sufficient  water  and  mix  slowly,  first  to  a  good  mortar,  then 
add  sufficient  water  to  bring  the  mortar  to  the  required  con- 
sistency. By  this  method  a  more  thorough  adhesion  of  the 
cement  to  the  sand  can  be  obtained.  Some  one,  some  day, 
may  perfect  a  mechanical  device  for  doing  this  satisfactorily, 
but  at  this  time  no  such  method  is  known.  The  rocking  trough 
has  been  tried  for  the  mixing  and  discharging,  but  invariably 
the  cement  will  flow  out  first,  then  follows  the  sand  to  fill  the 
upper  parts  of  the  joints;  therefore,  the  safest  way  is  to  use 
the  scoop  shovel  as  the  specifications  direct. 

Ten  days  is  the  minimum  time  for  keeping  the  street 
blockaded  and  free  from  traffic.  Thirty  days  would  be  better, 
and  longer  if  it  were  possible.  In  testing  laboratories  the 
usual  time  for  allowing  cements  (neat  cements  at  that)  to 
stand  before  applying  the  tests,  is  twenty-seven  days.  There- 
fore, when  you  open  a  grouted  street  to  traffic  in  ten  days  you 
are  demanding  and  expecting  more  from  the  cement  than  any 


VITRIFIED    PAVING    BRICK.  121 

testing  laboratory  would,  so  the  streets  should  remain  closed 
as  long  as  a.  suffering  public  will  permit. 

It  is  urgently  insisted  that  in  no  case  shall  the  proportion 
of  cement  be  lessened. 

Grouting  thus  finished  must  remain  absolutely  free  from 
disturbance  or  traffic  of  any  kind  for  a  period  of  ten  days,  at 
least.  These  specifications,  closely  and  skillfully  followed, 
will  give  you  the  three  important  factors  of  a  desirable  city 
thoroughfare— DURABILITY,  COMFORT  OF  TRAVEL,  PER- 
FECT SATISFACTION. 

The  foregoing  are  some  of  the  many  reasons  why  the  above 
instructions  for  brick  street  building  should  be  embodied  in 
all  specifications  by  the  authorities. 

One  of  the  greatest  difficulties  experienced  by  engineers 
in  securing  a  compliance  with  specifications,  is  the  fact  that 
details  more  often  than  otherwise  are  left  to  foremen  unac- 
quainted with  directions  found  in  the  specifications. 

It  has  been  found  in  the  experience  of  many,  that  if  the 
contract  for  the  performance  of  any  particular  work  embody 
a  requirement  that  all  foremen  on  the  work  be  supplied  at  all 
times  and  that  they  be  familiar  with  specifications  and  di- 
rections covering  the  portions  of  the  work  with  which  they 
are  charged,  a  strict  compliance  with  all  the  details  is  more 
easily  secured. 


ieAYLORO  BROS.  Inc. 
Syracuse  N.  Y. 
Stockton,  CaBf. 


I?  5  63 


T 


